In a dark jungle, black robed men, soldiers with masks on and knives on their ankles, accompany a tall statuesque woman, Lady Adrasta, and her older vizier, Karela, to an opening in the ground. A horn is blown and a man in black robes, begging for his life, is thrown into the pit.

In the TARDIS, K-9 reads "Peter Rabbit" to the Doctor, who sneezes as Romana pulls a crate of what she calls "old junk" out of the Number Four hold. She pulls out a ball of string which the Doctor used once. There is a note of thanks for helping Thesseus and Ariadne out of the Minotaur's maze. He snaps that the wretches were going to unravel his scarf and use it to help them get out of the maze. Romana asks what possible use the jawbone of an ass would have. The Doctor just tells her not to be a Philistine. She also pulls an MK3 Emergency transceiver which hasn't been used since the Doctor calls it a nuisance -- Romana takes his meaning to be that he was always getting calls from Gallifrey. He calls all that a bore and tells her he is never in distress -- or rather not often in distress as he must admit since she's quite sceptical. Romana plugs the transceiver into the console and the TARDIS shakes.

Romana switches it off but the TARDIS has landed and the viewscreen shows a thick jungle and a strange object with a flat side and many angles. K-9 stays inside but the other two go out past mist to the shell which the Doctor calls an egg or part of an egg, figures is semi-metallic, and is alive. He hears a transmission -- the same noise they heard in the TARDIS before they landed. Romana moves around to the other side while the Doctor stays and examines it with a stethoscope. He deduces it is a shell and a transmitter, and the shell looks woven. Bush-tumble weeds sneak up on and knock down the Doctor who ends up lying on his back, calling Romana for help. He calls her more urgently but a dark red and black dressed soldier stands over him. A Huntsman whips the wolf weeds off the Doctor, who thanks him but the Huntsman orders his men to kill the Doctor. He asks them instead to take him to their leaders. Before they can kill him Karela arrives and tells them to wait, something the Doctor repeats and then he thanks her. The wolf weeds are grown in Lady Adrasta's nurseries. Karela explains the Doctor is in the place of death; she tells him that anyone found here is put to death. He wonders about place names and hopes she will make an exception on his part. She tells him they have his commander -- which is Romana. The Doctor waves to his commander and tries to take her into the TARDIS, "It travels. We travel in it." Karela has her men stop them from getting into the TARDIS, "I hope you're not lying, Doctor." They put him in a portable woodstock which goes around his hands and neck. Lady Adrasta will want to see him. "All she had to do was make an appointment" retorts the Doctor.

As the group moves on, the Doctor realizes they are being followed. Scavengers attack, clubbing guards down, knifing the soldiers dead, and getting Romana away. The Doctor knocks a few down with his wood stock. Karela sits back on her chair and the men carry her.

The Scavenger leader, Torvin, a chubby, bearded messy man, admires his collection of metal in some old tent as Romana is brought in by his men, who include the younger Ainu and the older Edu. Torvin, Ainu, and Edu are former miners. Ainu thinks Romana is a Lady In Waiting from Adrasta's Palace. Torvin wants her killed since she has no use and no metal on her. The others tell him they want to vote on whether or not they should kill her.

The Doctor waits as Karela goes to get Adrasta from her throne room. He tells the guard he has an itch on his nose. The guard scratches his own nose but the Doctor gets both guards to come over, one scratching his nose. He then knocks down both of them with some karate. He is about to leave when Adrasta returns, offering her clawed and sharp nails to scratch his itch for him but he declines. Adrasta has been told the Doctor was found in the place of death. The Doctor is about to tell her something fascinating about the place -- but finds Adrasta already knows that anyone found there is put to death.

Adrasta takes the Doctor to her throne room where younger ladies stand at attention. She asks about the egg and mentions his commander. He tells her Romana is his companion. Adrasta tells him that she knew anyone of his intelligence wouldn't be in a subordinate position. She sends guards to go find Romana.

In the tent, Romana is tied to a stake. Only Ainu votes not to kill her. Romana tells them to go ahead and kill her -- they would be committing suicide, calling the leader a hair suited moron who wonders what that means. She tells him it means hairy. She is not from Adrasta, she explains, "I'm a Time Lord." Using her regale voice, she makes them untie her and sit down, then takes out her dog whistle which they like since it is metal. The men all have a turn trying to blow into it and Torvin succeeds. K-9 comes out of the TARDIS, answering the continuing blowing with some impatience, "Coming. Coming!"

Behind Adrasta's throne seat is a strange object almost like the shell -- the same design. She tries to keep the Doctor's interest away from it, wanting to know more about the shell outside which was found 15 years ago. The Doctor tells her it is screaming in pain -- a scream which can only be heard on low frequency wavelengths. He imagines what is it calling for, "By the pyramids, imagine the size of its mummy."  Adrasta snaps her fingers and two men, Doran and Tollund, pop out of a curtain, having been listening to this exchange between Adrasta and the Doctor. They are engineers. Tollund wonders about it being an egg of a bird -- the bird would be enormous and have a one mile wingspan. The Doctor tells them that not only birds lay eggs -- fish and reptiles do. The engineers and Adrasta ask about the heat on the shell. The Doctor suggests that "maybe someone tried to fry the egg!" Doran tells the Lady that this man is being facetious and the Doctor says "he's quite right!" The Doctor claims to have a teaspoon and an open mind which is why he found out more about the egg than Doran. Adrasta has Doran taken away with the Doctor following so he can see what happens to people who disappoint her. A guard who wants the Doctor to go ahead of him, waits for him and waves him on. The Doctor smiles, "How nice to meet a well mannered guard."

In the tent, Romana calls the bandits a duff bunch. One takes this to mean they have impressed the lady. K-9 arrives. Romana tells the scavengers she hopes they don't meet again, " I can't honestly say it's been a pleasure. Good day." As she tries to leave, K-9 has to stun Torvin who tried to stop her with his knife. She tells the rest he is just stunned and will wake up with a sore head, "I expect you're used to that."

They arrive at the pit - which they call "the Pit" -- and the horn is blown. The Doctor pleads with Adrasta not to kill engineer Doran even though he may be a bit of an idiot, "...even bad engineers are hard to come by on this side of the galaxy." Doran is thrown into the pit. They hear noises of the thing in the pit and a green glow comes onto Doran's face.

Romana arrives with K-9 who has to shoot an attacking guard -- who falls into the pit and dies. The Huntsman snaps his whip to get the wolf weeds to attack the dog. K-9 rays guns one of them with his nose laser but too many more arrive and cover him. He seems to whine and lose power. Adrasta tells Romana he is dead. She cries over him. Adrasta goes to the Doctor, "Well, Doctor, now I have you both -- now you're bound to be cooperative." The Doctor hugs Romana a bit and then races to the wheel over the pit. He grabs the rope on it and jumps into the hole. The rope runs out and the Doctor seems to plunge downward...

Romana looks over the pit edge and sees the Doctor holding onto to some rocks below. She asks to go down to the Doctor, who has begun to rock climb using a hammer, chisel, and spikes. The Doctor hears some creature below and reminds himself to not be afraid.  Romana begs Adrasta to save the Doctor. K-9 is not dead as Adrasta told Romana but he is webbed up by the wolf weeds and cannot help. He calls Romana and Adrasta is impressed that K-9 is metal. She goes to the hole and kicks dirt down it, "Pity you were such a fool, Doctor, I could've used you, too." Dirt hits the Doctor and backs him up so much that the spike he is on falls.

On the bottom, the Doctor finds the guard dead, and Doran, apparently dead of fright. He sees skulls and hears low moans of the creature.

Romana is brought to the throne room of Adrasta who tells her the name they have for the creature is "The Creature." Romana says that's original and asks if the monster is a native from this planet, Chloris. Adrasta avoids Romana's questions and looks in a mirror, handed to her by a servant girl. Since the Doctor left them, Adrasta has to keep Romana alive now. Romana asks her more questions but Adrasta tells her there are some questions better not asked. When Adrasta asks Romana questions, Romana responds with the same comment until Adrasta slaps her across the face. Metal here is valuable so Adrasta orders her guards to "break up the tin dog."

In the caves of the old mine, the Doctor finds green, glowing glop on the walls. He lights a match and comes face to face with an old man in robes.

In the throne room, Romana watches as guards begin hitting K-9. She will cooperate and tell Adrasta what she wants to know about the shell only if the guards will stop banging away at K-9. She tells Adrasta the information is in K-9's memory, which makes Adrasta, in anger, call the guards off. Adrasta tells her that this little metal animal makes both Romana and the Doctor redundant. Romana doesn't think so...only she can operate K-9.

The old man in the cave, Organon, leads the Doctor to a safer place of wood and rock. The place is illuminated by candles in half skulls. He tells the Doctor something about his mother being under the sign of a Praxus, about her being a middle cousin or some such prattle, and that she taught him not to let anyone be eaten alive if he can help it. The Doctor introduces himself to Organon, telling him his mother must have been a very fine woman. Organon was Adrasta's Seer, a court astrologer, although he has been to other courts and sold them on his being able to see into the future, "Astrologer extraordinary. Seer to princes and emperors. The future foretold, the past explained, the present...apologized for." He basically tells the Doctor his act is just an act. He has survived by eating the scraps of food the serfs or servants throw down, an offering they make to the creature, he supposes. He asks the Doctor how he sees into the future and what he uses -- the stars, a crystal ball, or something else. The Doctor tells the truth, "Oh, I tend to use the Police Box Affair." Organon's prophesy, of the Lady Adrasta getting visitors from beyond the stars was what made her throw him down the pit. Organon asks the Doctor where he is from. "Oh, from beyond the stars," he answers. They wonder why Adrasta would be afraid of something or someone from beyond the stars.

In the Scavenger's tent, Torvin gets up and makes plans to ransack Adrasta's palace since she is the only one to have mineral and metal wealth on this planet.

In the cave pit, Organon explains he has managed to avoid the creature. These caves were mines which were worked out of metal. Metal is scarce on this planet. Adrasta owns the only mine there is. She depends on the shortage of metal for her power. Organon's horoscope told him he was going to be useful to somebody today... he thought it was going to be the creature - which is about 200 feet tall. At times, it sounds as if it is crying, singing, or growling. He thinks there is only one but the Doctor wonders how he knows that. He thinks the planet is very beautiful but the jungle and forests make it difficult for anyone to travel far. As they talk, the creature's blob body comes to the door to Organon's little place.

In the throne room, K-9 confers with Romana. He can stun the guards but is not mobile. Karela doesn't trust the girl or the tin animal and pushes Adrasta to kill Romana. Adrasta tells her later. Romana picks up K-9 who stuns the guards down but other guards grab her and pull K-9 from her arms. One guard has his long knife to Romana's throat. Adrasta stops him from killing her, calling that an invaluable demonstration.  Adrasta throws Romana at K-9, wanting her to make K-9 behave.

In the cave place, Organon has a candle skull which the Doctor moves at the monster to see it. It moves away. Organon closed his eyes and is startled when the Doctor touches his arm. Organon thinks this is the Doctor's Lucky Day -- and asks what sign he was born under -- Aquatraian, Ariel, or others. The Doctor asks if he ever felt its skin to which the old man answers "I was rather trying to avoid it touching mine." To the Doctor it looks as if its skin is like the cerebral membrane which protects the brain in humans. The Doctor wants to go after it and leaves. Organon decides to remain behind and tells the Doctor so. But after the Doctor leaves, he decides to follow.

In the throne room of the palace, Adrasta asks K-9 about the TARDIS. With it, she tells Karela, they can go anywhere, anytime and get pure metal. She will still have the monopoly on metal here. Karela says it's a pity the Doctor is no longer with them. When they talk of his demise, Karela isn't sure, "He struck me as most resourceful for a man." She will take guards and go into the pit to make sure the Doctor is dead. Karela will also kill the thing in the pit, just for Adrasta, her lady. Adrasta doubts she can and orders K-9 to kill it, calling him tin. He corrects her and tells her he cannot kill -- unless in defense. Adrasta tells him she can see to that. The TARDIS makes the creature in the pit superfluous now and she wants it dead. Karela warns K-9 that he will do as they say. There are three doors to the pit from the palace, one behind the throne, all three bolted on the palace side. A guard carries K-9 in, followed by Romana, and then the Guard Master and two men go in, Karela follows, and lastly, Adrasta joins them, putting herself last for her own safety.

Organon, in the pit caves, tells the Doctor not to move too fast. The Doctor doesn't know what they are going to do when they find the monster. Organon is upset but the Doctor tells him he has a plan -- he just doesn't know how to apply it. As they talk, the monster looms over them, gigantic, and glowing green. Organon looks up at it, "Fine time to tell me." They move back slowly as the Guard Master and his two men arrive and fire at it with bow and arrows! The guards move back and away. This gives the Doctor a chance to move forward. He hands the candle-skull to a protesting Organon and pats Organon's hand to calm the old man. He moves at the monster. Organon calls, "Doctor, come back."

Organon moves to the Adrasta guard master and his two men, telling them they must help the Doctor but a light from the creature moves them back out a hole and the light forms a new shape covering the door, a shape just like the egg shell formation and the formation behind Adrasta's throne. It is hard as rock and Organon wants them to get the Doctor out and they try. They hear a knock which Organon knows is the Doctor -- knowing, he tells the guards, is his profession.

Outside the Palace, Ainu reports that Edu is going to talk to the guard; then they overhear Edu stab the guard.

In the caves, Romana whispers to K-9 to be ready.  Karela moves to get her away from the tin animal but Adrasta believes or makes believes she trusts Romana, much to Karela's fear. They get the news about the Doctor from a guard. Another guard lifts K-9 off a rock and down to the floor.

In the entrance room of the palace outside the throne room area, Edu stabs a guard in the back, killing him. He opens the door for the other scavengers.

In the cavern cut off from the rest, the Doctor finds other minerals not from the mine -- cadmium and malgavic iron. He puts his match out and waves the creature which just let him go. He calms it, telling it he is not armed and he won't hurt it. He says its skin is beautiful and extraordinary. He figures it has green veins and lives on chlorophyll -- which makes Chloris the right place for him to come to. He puts his hand on it, calling it a good girl and a good boy. He figures that it has no eyes or mouth -- but that he can see. He listens to its side, pressing his ear to it, thinking possibly telepathy can help him make contact. He pats it and then looks into and then blows into the large tentacle thing coming out of it. He also talks into it. The tentacle points to the shell over the door -- perhaps pictures can help them communicate. It glows and makes the shell glow, the molecules around the shell's outer surface move.

In the throne room, Torvin calls a guard over, showing that he is not armed. His other men trip the guard and stab at him with their knives and hit him with clubs or spears. They take bronze and iron, then see the strange object behind the throne -- Edu feels it and it is warm but when Torvin touches it, he finds it less so. They take it and exit one of the doors to the pit.

The Doctor knows the creature wants something but asks if the object is a weapon, "I wish I knew how far I can trust you." The Doctor will get it but first starts to ask the creature to promise him... but realizes that is a stupid thing to say. He finds smaller egg-shell objects in the pit but the blob won't let him take any of them. He pulls his scarf along the dirt as he leaves, almost as if he wants to pull one away with him.

On the other side of the door, Romana finds Organon telling her that his friend is trapped in there. She tells him she knows the Doctor and he asks the celestial circumstances of his birth. She tells him that the Doctor claims to have been born about 750 years ago, "..so he says." Adrasta arrives and asks Organon why he hasn't died. He says it was an oversight. The Guard Master tells her they cannot get through but she threatens him, using his commission. Other guards are told by Adrasta to keep Organon here as he tries to leave. K-9 repeats he is programmed not to kill, only in defense. Romana tells him to his best on the door.

In the cave, Torvin is examining a zinc candle holder, but when he and Edu hold up the shell object, it seems to trance Torvin and Edu, who hold it up higher and take it off toward the cave area where the Doctor is.

K-9 tells Romana his power packs are almost depleted and he needs power. The material around the door entrance only self renews itself every time it is damaged or shot at by K-9. The atoms recombine and the molecules reform to get stronger. Adrasta wants to keep blasting at it but Romana tells her they must think. She knocks on it, wondering how they are going to get through it. Seconds later, the Doctor comes smashing through it to their area. Adrasta demands to know how he got through. He asked the creature very nicely but she slips and reveals she knows the creature cannot talk. The Doctor goes to Organon who asks his sign. The Doctor tells him the sign of Crossed Computers was what the Doctor was born under -- the symbol of the Maternity Service on Gallifrey. Adrasta order Karela, Romana, and guards and go to the creature to kill it. A guard stops the Doctor from interfering by holding a sword on him. K-9 is drained so Romana has to carry him. After they go, the Doctor tells her she's sent them to their deaths. He also tells Organon that Adrasta's evil eye is upon him. She stops the Doctor from going to find out what is happening and demands Organon to go. If he doesn't go, her guards will cut his throat from ear to ear. The Doctor tells him to find another line of work, astrology is not his forte.

Romana and Karela return to them. The creature is gone -- it must have found a passage in the back of the cave. Adrasta warns Romana to hold K-9 facing the rock walls. She demands to the Doctor that K-9 kill the creature -- which she calls a Tythonian. He responds, "Oh, but he's only a little dog." Karela will kill Romana if he doesn't obey. She turns K-9 toward the Doctor who pulls out a mirror for K-9's laser to bounce off of and hit the guard attacking Romana. K-9 also shoots the guard ahead. Karela runs away, getting out. The Doctor warns Romana not to try to follow Adrasta, who also flees but doesn't get far. The monster blocks the exit she was trying to run through. The Doctor grabs her and pushes to it more -- she knows the monster doesn't eat people; she knows what it eats and Organon agrees with the Doctor about Adrasta. Adrasta gets a knife out and to the Doctor's throat, ordering Romana to train K-9 on the monster. The Doctor tells Romana not to do it but she only has six seconds before Adrasta kills the Doctor.

Torvin and Edu run away. K-9 is told to blast Adrasta if she moves. The Doctor, Romana, and Organon go to the object. When the Doctor touches its extension, the blob talks like the Doctor, communicating using his larynx. At first, this confuses the Doctor and Romana.

In the throne room, Karela calls a guard to get the Huntsman.

The blob uses the object to talk to the Doctor, "Do not be alarmed or frightened." Erato, the name of the Tythonian blob, does not have a larynx. Romana asks why he is skulking about in a pit eating people. The Doctor looks at her, "Oh please, you put that so crudely." Erato eats chlorophyll and mineral salts. He came to this planet on a trading mission. Weeds come over K-9 and hold him. The Huntsmen arrive and Adrasta can move again. She orders the Doctor to have K-9 kill Erato or his "friend" Organon dies. The Doctor moves to shake Organon's hand, "Organon, good bye old man, so sorry about all this." He moves back, away from the old man, who is shocked.

Erato must not die. The well being of two planets hangs in the balance. The Doctor yells the situation to Adrasta and to the Huntsman -- all they have on this planet are weeds, weeds, and more weeds. They can't plow the land because they have no metal. Adrasta yells at the Huntsman not to listen to the ravings of a demented space tramp. The Doctor calls her a pathetic woman who does not have a care for her own people. The Huntsman lets the Doctor speak. 15 years ago, Erato came to Chloris to trade metal for chlorophyll but the first person he met was Adrasta who did not care for the welfare of her people. She tricked Erato, an ambassador from Tythonus, into the pit and "threw astrologers at him." To prove what he says, the Doctor wants Adrasta to take the communicator. She orders the Huntsman to kill the Doctor. He, instead, wants her to speak to the creature and whips his wolf weeds to make her. She is forced to take the communicator and her voice comes out, "Thank you, Doctor." Adrasta did trick him into the pit. Adrasta runs and the wolf weeds start to kill her. Erato covers the wolf weeds and Adrasta, who may have been dead already. Erato eats the wolf weeds -- his first solid meal in 15 years. The Doctor checks Adrasta and with her die the dark ages of this planet, the Huntsman feels. Erato is sorry for all this unpleasantness. The Huntsman thanks the Doctor but the Doctor tells him not to say that yet.

In the throne room, with K-9 and Romana, Organon complains that the Doctor was going to allow him to be killed because he would not order K-9 to kill Erato. K-9 verifies all this. Romana tells him that the Doctor wasn't going to allow Organon to die, he probably checked his horoscope. The Doctor comes rushing in just then -- he did check the horoscope, he says, and found Organon is going to die of indigestion. Erato is taken out of the pit by the Huntsman and his guards. Romana asks the Doctor if it is safe, and if Erato is telling them the truth or lying. It has no intention of crushing people -- it was just trying to contact them and in the pit, it accidentally killed people. It just wanted to communicate. Erato came here in a giant egg, which parts they have seen, and when the parts are put together, form a spaceship with a photon drive. The pieces called out a distress signal. Organon brings in charts and puts them on the table. K-9 knows that Erato's people live for about 40,000 years. 15 years are but the wink of an eye to them. Romana keeps asking the Doctor questions but answers her own while he keeps responding with the word, "Yes." She asks if he can say anything but "yes." to which he answers once again, "Yes." The Doctor keeps asking Romana questions now about the situation which she responds with, "Yes." He has taken the photon drive without which the alien cannot leave the planet. The Scavengers hear this, listening from outside the window.

The Scavenger Ainu tells them that from what the Doctor said they can make it big if they steal the photon drive.

Inside the throne room, the Huntsman comes to Organon and they consult the astrological signs. The Doctor gives Organon the photon part. The Huntsman goes to the room where Romana is on the communicator, making Erato use her voice to talk. It tells them the whole truth now. They all have 24 hours to live. A neutron star is on its way to plunge into Chloris's sun in 24 hours, retaliation from his people for Adrasta's putting him in the pit.

Organon looks at his charts in the other room, "Oh dear." He reads that something terrible is about to happen. He is hit from behind the head and someone takes the photon drive piece.

The Huntsman, Romana, K-9, and the Doctor continue to talk to Erato. There is no way of stopping the star, Erato claims, also stating that he wishes to leave, not wanting to see this distressing finale. He will build a new ship which will take 26 minoyos -- one hour and seven seconds by human standards. The ship has Aduminum in it.

The scavengers arrive to their tent with what they stole.

At the palace, the Doctor figures a plan and removes ticker tape from K-9 -- if Erato spins a thin shell of aduminum around the neutron star (a collapsed star), the TARDIS can be used to yank the star away from Chloris's sun. Erato claims he will not do it for a people who put him into a pit. The Doctor makes him see that it was because of one person -- Adrasta -- and a whole planet should not suffer because of one person. The Doctor also makes him see that he came to this planet for his own good... to get something from it. The Doctor explains about the part after Erato agrees. Erato asks the Doctor what he would have done if he did not agree to this. The Doctor fumbles about for words, "My dear old thing..."

Romana is sent to get the piece from Organon but finds it gone.

In the tent, Torvin is still musing over his loot he has all the metal he wants now -- the monopoly will be his. Suddenly, he gasps as Karela sticks what she calls "six inches more to add to his collection" -- her knife -- into his back. He dies, looking at her knife which he sees is tempered steel. She stops the others from killing her by telling them she has the piece hidden. With it, they will not only have the monopoly but can force Erato to make more shells. The Doctor comes butting in at what he calls an indelicate moment. Karela tells them to kill the Doctor but he yells at them to wait. He tells them the truth about what will happen to this planet and this solar system. The Huntsman comes behind Karela and grabs her. She will not tell them where the piece is. The Doctor throws all the iron and metal onto the floor, off the table. He asks Karela is she is willing to sacrifice the lives of everyone on this planet for wealth and power. She cackles yes to him. He makes K-9 nose-laser the metal into dust.

They get the fragment and Erato takes off. Soon, Romana, K-9, and the Doctor are in the TARDIS with the communicator. Romana computed their chance of success. The Doctor snaps, "I don't want to hear them."   "Very wise," Romana retorts.

Erato is in space and the TARDIS soon joins him. The Doctor has Romana activate the gravity tractor beam but then deactivate it -- they can only hold it on five seconds at a time. K-9 has his antenna hooked up to Erato and communicates to it as it uses his voice! Erato begins weaving around the Neutron Star as the TARDIS holds it and pulls it, shaking uncontrollably and lighting up as if the star were affecting it. There is an enormous strain on the TARDIS and a blast occurs which makes the gravity beam stuck on the on position. This makes the star become drawn to the TARDIS which dematerializes at just the right moment. The star goes hurling off into space, away from the sun of the planet Chloris. Romana figured their chances at 74,384,338 against. The Doctor claims this is his lucky number.