A circus owner called Rossini lights a cigar, and is surprised when a horsebox appears out of nowhere. From within the horsebox, a man dressed in all black, with a neatly trimmed beard and moustache. He informs the circus owner that he is called the Master. The Master hypnotizes Rossini, and he follows at the click of the Master’s fingers.

Inside a museum, is the last fully surviving Nestene Energy Unit that remained fully in tact after the last Nestene invasion is closely watched and protected with a glass cage. The Master smashes the glass surrounding the Nestene Energy Unit, the guard tries to raise the alarm, but Rossini attacks him from behind, leaving the guard on the floor and unable to defend the missing Nestene Energy Unit.

The battered blue Police box, stands in the corner of the Doctor's laboratory, looking like it has been through the Asteroid Belt. Smoke creeps out the door, followed by a coughing and spluttering Doctor, who has bought the dematerialisation circuit from the Police Box. The Doctor carefully places it and is ready to start some tests on the circuit when there is a knock at the door. "Not today thank you" says the Doctor, confusing the young girl who has walked in for the tea lady. The young girl is called Josephine Grant. At that point the test that he is trying to perform causes a small flame and lots of smoke. Jo garbs the fire extinguisher from across the room and starts tackling the fire. Satisfied that the flame has gone, she stops the fire extinguisher. The Doctor is annoyed as this girl has spoiled six months delicate work and explains that Steady State Micro welding always causes more smoke than fire. Still confusing Jo for the tea lady he again says to her that he doesn't want any tea today. Jo finally tells the Doctor that she his new assistant and also apologizes for damaging her experiment. The Doctor is very worried that somebody who damaged his experiments will be his new assistant even though he accepts her apology. Jo then tells the Doctor that the Nestene Energy Unit has been stolen from a museum and wonders who would steal it and why?

A man named Philips who is dressed in a suit is climbing a radio telescope station and greets a man named Goodge who is wearing a white coat and working at an electronic unit. Meanwhile the Master is lurking outside. Philips thanks Goodge for some results that he has given him. Philips then goes back down the radio telescope. Goodge then gets out a lunchbox and a flask. The Master enters and points a black tubular device at Goodge. He presses a button and a brilliant white light flashes from out of the end. Philips sits down at a desk, blatantly unaware of what is going on at the radio telescope.

Back at the radio telescope, the Master gets a green tin with UNIT markings on it. He opens the lid to reveal the Nestene Energy unit. He then attaches two patches either side with a wire linking the unit with the electrical equipment. The Master then turn's two black wheels in the same direction and this make the transmitters move.

Philips noticing the movement is surprised and tries to contact Goodge to ask him what is happening only to get no response. The Master is though ignoring the pleas of Philips who is trying to talk to him via a radio. Philips then leaves for the radio telescope where he left Goodge to find out what is happening.

In the Doctor’s laboratory, the Brigadier enters only to be confronted by an angry Doctor, who is mad at having Jo as a new assistant. The Brigadier says to him that he will reassign her but that he should break the news to her. At that point Jo diffuses the situation by walking and reporting to the Brigadier that there is no news about the stolen meteorite and tells the Doctor that the electric spares that he wants will arrive tomorrow. The Doctor then tries to tell Jo that she is not wanted but can’t bear to say the words and ends up saying thanks to her saying that she will be useful to him. Jo then also report the mysterious goings on at the radio telescope and also that two scientists have gone missing.

The Doctor, Jo and the Brigadier drive to the radio telescope, and they are greeted by Captain Yates, who introduces Jo and the Brigadier to the director, but the Doctor is at the top of the radio telescope, and is surprised to hear the noise of a TARDIS materializing. A man appears, and calls for the Doctor. He is a Time Lord and has come to warn the Doctor about the Master, who has appeared on Earth. He also explains that the door to the control room has been rigged so that a bomb will fall on the floor, and explode. The Doctor bursts through the door and catches the bomb before it lands on the floor. The Doctor diffuses the bomb.

The Master enters a small office, run by Mr. Farrel. Farrel runs a plastic factory, which his father has set up. The Master, going under the name of Colonel Masters, says he represents people who need a lot of plastics.

The Doctor, having just finished explaining what a Nestene is to Jo and Mike Yates, believes that the Autons and Nestenes have already arrived on Earth. The Doctor asks Mike to make a search of all the known plastics companies.

The Master hypnotizes Mr. Farrel, while the Doctor boils the contents of the bomb.

Jo arrives at the Plastics Company owned by Mr. Farrel, via a back way, so that she doesn’t get caught. Unfortunately, the passing Farrel and the Master catch her, after knocking over some boxes she hid behind. Jo is hypnotized by the Master, and he tells her that she must tell her superiors that everything is in order, and that she only met Mr. Farrel plus some unheard instructions.

Mr. McDermott, an assistant to Farrel, encourages him to go home, as he believes Farrel is ill. When Farrel leaves the room to go and find Colonel Masters, McDermott asks his secretary, Sylvia to get Mr. Farrel Snr. Meanwhile, Farrel Jnr enters a small room where an Auton is about to hit him. The Master intervenes, asking why Farrel came here.

Benton grabs Jo, taking her away from the bomb, and the Doctor takes the bomb, and throws the bomb out of the window, causing a massive explosion, with water flying everywhere.

Mike Yates asks the Doctor, what’s wrong with Jo. She is deeply traumatized after doing something against her own free will, which the Master can achieve, however some minds can resist hypnosis.

McDermott is in the office, with the Master and Farrel Jnr, who is annoyed at the Master’s methods, as an entire day’s production has been ruined. The Master takes out a folded, black, plastic chair and clicks his fingers. The chair opens, and he asks McDermott to sit in it. He sits down, only for the chair to start moving. Farrel goes to help him, but the Master, who will not tolerate his interference, stops him. The chair crushes McDermott to death.

The Doctor tries to get Jo out of the deep trauma, which Jo, after much trying, does. After reassuring her, the Doctor tries to find out what happened to Jo. She recalls being an office, and a voice telling her to open the box, but she can’t remember who told her.

Mr. Farrel Snr has arrived, and is upset at the demise of McDermott. The Master sees Farrel Snr as a threat and tries to take over him, initially there is no resistance to hypnosis, but then he resists, and the Master, frustrated, walks out of the room. After which, Farrel Snr tries to get his son to take a few days off, but fails. He also demands that production goes back to normal and Colonel Masters left. The Master has walked out to Mr. Farrel Snr’s car, and he opens it, placing a red troll doll in the car, and also turning the heating up. He then catches up with the elderly man, and shows him the doll, which Farrel Snr believes there is no demand for, and he drives away, with the doll in the back of his car.

The Brigadier walks into the laboratory, and Jo starts apologizing for trying to kill them off. Yates walks in and tells the Brigadier that they have found Philips’ car, where a circus used to be. The circus has been relocated, which leads the Doctor to take photos of Philips, and go and look for him, but Jo is told to stay in the laboratory.

In Mr. Farrel Snr’s car, the troll doll that the Master put in, has come to life. He opens a window, turns the temperature down, and the doll collapses. Meanwhile, the Master tells Farrel Jnr to make maximum output of the Autons. Farrel is worried that his father will cause trouble, however the Master tells him that he persuaded him to change his mind.

Bessie, the Doctor’s yellow roadster pulls up into the circus. Once the Doctor has left to try and find Philips, Jo emerges, having hidden in the back. The Doctor doesn’t have any luck finding Philips.

Mr. Farrel Snr is talking to his wife, telling her of the lack of concern from Colonel Masters and Farrel Jnr, and his wife hopes that Rex will get rid of Colonel Masters. She is even more disgusted after seeing the troll doll.

The Doctor keeps looking for Philips to no avail, and he goes into a horsebox where Rossini immediately catches him. Jo observes all this. Rossini is taken to a small caravan, where he is tied up by Rossini’s henchman, Tony, a big tall strong man. Rossini asks why he was interested in his friend’s horsebox. The Doctor doesn’t answer, and eventually, Tony attempts to twist the Doctor’s arm. He tells him that he was listening for vibrations. Rossini eventually pulls out a photograph of Philips, but Rossini is pretending to have no idea where he is. Meanwhile, Jo rings the Brigadier, and tells him of the Doctor’s current predicament and Philips is seen entering the horsebox.

Mr. Farrel Snr’s wife goes off to make some coffee. The doll, which is on the radiator, starts to rise again. It moves over to Mr. Farrel and kills him. His wife enters, and is horrified at what she sees.

Rossini is angry with the Doctor, and decides he needs a breath of fresh air. The Doctor decides to try to call for help, when Tony stuffs a handkerchief in his mouth. Jo storms in and smashes a vase over Tony’s head, and he falls to the ground. Jo unties the Doctor, and tells him that he has seen Philips enter the Master’s TARDIS.

Philips, from inside the Master’s TARDIS, tells the Master about the Doctor & Jo, he then goes out looking for them. He goes into the caravan, holding a grenade. The Doctor tells Philips to resist them, and in the end, Philips is confused and forgets to throw the grenade away, killing himself. Doctor enters the Master’s TARDIS and borrows the dematerialisation circuit. A mob, led by Rossini goes up to the Doctor & Jo, and strike the Doctor. A police car, followed by the Brigadier and Yates eventually rescues them. Inside the police car, the Doctor recovers.

Benton tells the Brigadier that the police car that took the Doctor & Jo is not a police car after all.

The Doctor attacks the Auton, and runs out of the car with Jo. They hide behind some rocks. Another car appears, this time containing the Brigadier and Yates. The Brigadier gets out of the car, and starts shooting at the Autons, he s encouraged to get down by the Doctor. Yates drives the car around, knocking the Auton down an embankment. Yates drives that car round to where the Doctor, Jo and the Brigadier are, and they drive off, avoiding the bullets of the Autons as they go.

Farrel enters the office, and sees the Master, looking out of the window. He tells him that the Autons failed to kill the Doctor, and the Master already knows.

The Brigadier is holding a conference at UNIT HQ, with the Doctor wandering around his laboratory. The Doctor informs the Brigadier that the Autons plan to occupy the Earth, although they have left the circus. The Doctor also suggests that the Autons that are here are just a diversionary threat, and that their main force is waiting to land. The Brigadier suggests redoubling security and finding the Master’s TARDIS, which the Doctor recommends. The Doctor fits the Master’s dematerialisation circuit in his own TARDIS and tries to take it for a test ride. He fails to take off, and a Doctor coughing at the smoke, comes out of the TARDIS embarrassed. His embarrassment turns to joy when he realizes that he has broken the Master’s dematerialisation circuit, meaning the Master is stranded on Earth.

Men in funny carnival masks are handing out plastic daffodils to anyone who wants them. With all the daffodils gone, they all head back to a coach, where they take off thier masks to reveal themselves as Autons. They ask Farrel to drive them to the next distribution centre, but he encourages them to wait for the Master, which they do.

The Brigadier introduces Mr. Brownrose who tells a worrying story of death’s rights across the country of asphyxiation, shock and heart failure. Only the first two deaths have something in common. Mr. McDermott and Mr. Farrel Snr who worked at the plastics factory.

The Doctor and Jo have gone to see Mrs. Farrel about Mr. Farrel Snr’s death. She went out to make some coffee, she heard a scream and found him dead. She tells the Doctor of his worry about the plastics factory, and she seemed to think that Rex Farrel had fallen under the influence of one Colonel Masters.

A telephone engineer is fixing the phone in the Doctor’s laboratory, when Yates walks in and asks to see a pass. The engineer uses a long flex, as apparently the Doctor likes to move about when he’s talking.

Mrs. Farrel shows the Doctor the new dolls that the Plastics Company has been making. She says that she originally put it on top of the radiator but then she found it underneath the curtain.

The Doctor has returned to his laboratory with the troll doll that killed Mr. Farrel Snr. He uses a scalpel to cut the doll open, and finds that it is completely plastic. He asks Jo to order some equipment, and then leaves with the Brigadier.

Mr. Farrel is ordered to drive on by the Autons, but says that they must wait for the Master. The telephone engineers from earlier turns up, and peels off his false face to be revealed as the Master.

Captain Yates has gone out to make some cocoa, and has put on the Doctor’s Bunsen burner. Jo is on the telephone to Mr. Campbell chasing up the supplies, when the troll doll starts to move.

The Doctor and the Brigadier visit the Plastics Company, and find no one there.

The doll starts moving towards Jo and attacking her, she shouts for Mike Yates, and he comes in and shoots at the troll doll, rendering it lifeless.

The Doctor and the Brigadier enter the main office, and find it deserted, apart from a plastic daffodil, which the Doctor finds on the floor, and asks the Brigadier to hold onto it, while he tries to open a safe. The Brigadier sees that Farrel has ordered a 15 seat coach. He walks over to look at a filing cabinet when the Doctor opens the safe, to reveal an Auton. It fires at the Brigadier, missing him, and the Doctor shuts the safe.

The Doctor calls for the Brigadier’s help, and he disconnects the telephone from the socket, and untangles the Doctor.

The coach with Farrel and the Autons are driving down a country lane, and are followed by a biker.

In his laboratory, the Doctor is applying heat to a plastic daffodil with a blow torch, but nothing happens, which disproves the theory that the plastic comes alive with heat.

The Brigadier orders a call to the RAF, having received some good news. He goes into the Doctor’s laboratory, where he tells the Doctor that the coach of Autons has been found, and they are going to bomb it. Captain Yates tells the Doctor and Jo they have an hour and a half to find out whether the daffodils are dangerous. Yates hands Jo a walky talky so they can stay in touch.

Farrel is looking out of the door of the coach, and the Autons informs him that they are being watched as they were followed.

The Doctor has converted part of a daffodil from Nestene symbols into visual symbols. It shows a face on the screen, but it is inconclusive. The Doctor asks Brigadier to delay the airstrike, as he needs more time. Jo tries to get hold of them on the walky talky, however the radio signal sets off the daffodil and it starts moving. Jo starts to examine it closer, however the daffodil sprays a mask over Jo’s face. The Doctor struggles to get it off and eventually, succeeds when he applies a spray. The Doctor asks the recovered Jo to see if there were any short waves radios were seen at the death.

Benton has a call from the RAF, which confirms the airstrike.

The Doctor wonders why the mask that was on Jo’s face wasn’t seen at the death. He breathes on the mask and it melts in his hand.

The Master enters the room, and is about to kill the Doctor to get the dematerialisation circuit. Jo enters and the Doctor threatens to kill Jo if the Doctor doesn’t hand him the circuit. The Doctor starts to hand it over when Jo begs the Doctor not to, as she blurts out that he’s beaten already as there going to bomb the quarry. The Master, in wake of this revelation lets them live.

The Doctor, Jo and the Master arrive at the coach with the Autons and Farrel in Bessie. The Brigadier desperately tries to get the airstrike aborted, and thankfully, the RAF just fly overhead without attacking the coach. Inside the coach, the Doctor sends a message using Morse code to the Brigadier saying "The daffodils are dangerous". Inside the coach, the Doctor and Jo have escaped from their bindings. The coach then drives off.

The coach is heading for the Radio Telescope, but Farrel realizes what is going on and tries to crash the coach in a nearby field. The Doctor and Jo escape from the coach.

The Master heads up to the Radio Telescope to prepare the signal for the Nestenes main party to arrive, while the Autons start firing at UNIT troops killing most of them. The Doctor and the Brigadier follows the Master up to the top of the Radio Telescope. When he reaches the top, the Master opens the channel for the Nestenes to arrive, and a big octopus type shape starts to appear. The Nestenes have started to arrive. The Doctor begs the Master to stop the Nestenes invading. The Master switches sides, and helps the Doctor close the channel for the Nestenes, so they are forced back to where they come from.

The Autons that are attacking the UNIT troops, start to look disorientated, and start to fall down one by one.

After they've closed the channel, the Doctor and the Brigadier realize that the Master has vanished.

The Doctor and Brigadier go back to the coach, where the Master has given up. He comes out with his hands up, and the Doctor warns everyone to be careful. The Master decides to make a move, but Captain Yates guns him down. The Doctor peels off his face to reveal Farrel underneath. The coach then starts to move, and is driven by the real Master. He tries to run anyone over, but fails miserably, and he moves off.