Baron Teufel is returning home after an absence of 20 years. Just before he left, there had been 14 unexplained deaths in the quiet German town of Orlok and in each case the dismembered bodies of the victims had been found close to his castle. His travelling companion, Klaus Lügner, points out that the killings stopped abruptly the same night that Teufel left. The Baron claims the murders were committed by the legendary Beast of Orlok, a creature said to have existed in the area during the Middle Ages, some 400 years earlier. He adds that the attacks stopped because he himself encountered the Beast as he was leaving town and killed it, suffering terrible facial scars in return. Lügner doesn’t believe him and says the Beast is nothing more than superstition - but then suddenly their carriage comes to a halt and one of the coachman tells them a tree has fallen across the road and is blocking their path. Lügner is suspicious of Teufel and pulls a gun on him, but then they hear the growl of a terrifying creature, followed by screams from the two coachmen. They listen as the Beast comes closer and turns its attention on the coach itself, then Teufel pleads with Lügner to open fire…

The TARDIS materialises and the Doctor and Lucie and are shocked to discover they’re not at their intended destination, Alton Towers! Lucie criticises the Doctor’s driving skills and suggests that next time he’d better let her drive as girls have a better sense of direction. He tells her the controls take centuries to master, but he does point out that if he was ever separated from the TARDIS she should press a big red button that would enable the ship to home in on his heartbeat. Just then they hear a gunshot and race off in the direction it came from…

The coach has been overturned and Baron Teufel is badly injured. A young man is looking after him and tells him to save his energy. Moments later, the Doctor and Lucie arrive and the young man explains that he stumbled upon the coach in the middle of the road. The bodies of two people and the horses are nearby, all ripped to shreds. The Baron appears to be the only survivor, but he’s trapped under one of the wheels. The Doctor examines him and discovers that although he’s lost a lot of blood, he doesn’t seem to have any obvious wounds. The three of them lift the coach off the ground and pull the now unconscious Baron away…

Two figures are watching the rescue from the forest nearby. One of them advises his companion, Wolf, to proceed with caution. He can’t tell if this is the man they’re looking for as it’s been so many years and his face may have changed. He suggests they patiently observe what’s going on, then when the moment is right they can take the man and the girl too…

It sounds like there’s a storm approaching, so the Doctor, Lucie and the young man work quickly before the rain washes away all traces of what happened here. The Doctor finds a walking stick caked in clay with the handle shaped like a wolf’s head to represent the Teufel coat-of-arms, but it’s been snapped in two. He also finds a letter from Grand Duke Albrecht which he puts in his pocket for later. Lucie thinks she can smell fireworks and wonders if the damage was caused by a bomb or a lightning strike or even a meteorite. The young man confirms they’ve had falling stars in the area before. He reveals that they’re in the Black Forest and the Doctor deduces from the evidence on offer that the year must be 1827. The man introduces himself as Hans Tod and says he’s a student. The Doctor concludes that the damage was caused by a large animal, bigger even than a bear, and Hans immediately recalls an old nursery rhyme about the Beast of Orlok. Suddenly and without warning, a nearby tree is hit by a lightning bolt and crashes into the road, and although everyone dives for cover, the Doctor is knocked to the ground.

The burgomaster of Orlok, Otto Pausbacken, calls together a meeting of the town councillors and tells them they’re facing a crisis. He reports that at 8.00 this morning, a carriage was discovered two miles away that had been smashed to pieces and three of the four occupants killed. The councillors, led by Grinsen, are dismissive of Otto’s concerns as he has a reputation for calling emergency meetings to discuss trivial matters, and they believe he overreacts to everyday problems. Otto warns them the accident was not simply caused by the storm. He tells them the carriage was flattened, the horses were thrown 30 feet in the air and two coachmen and a passenger were decapitated. He reminds the horrified councillors that they haven’t heard of such acts for a very long time, but it seems that after 20 years, the Beast of Orlok has returned.

To Lucie’s amazement, after she and the others were “rescued” by the burgomaster and his men, they were thrown in a cell. The Doctor is still unconscious and should really be in a hospital, but what really riles Lucie is the fact that the townspeople treated Baron Teufel like royalty and escorted him back to his castle, yet no one thanked them for saving his life. Hans says his mother won’t be happy when she finds out what he did as she’s not a fan of the aristocracy and thinks people are quite capable of governing themselves. Even though Teufel has been away for 20 years, the very mention of his name angers her, whereas his sister believes a resident nobleman would be good for tourism. No one really knows why Teufel left Orlok all those years ago, but Hans’s mother was even opposed to Hans going away to university to study philosophy just in case he bumped into the Baron and was corrupted by him.

The Doctor eventually wakes up and Lucie explains that the burgomaster had them thrown into jail because he suspects they had something to do with the attack on the carriage. Hans reveals that Otto Pausbacken has a reputation for stupidity, but his words are overheard by the burgomaster when he comes to question them. He tells Hans he has enough evidence to have them guillotined and it’s only his good will that’s saving them from that fate. Lucie insists that she and the Doctor had only just arrived, but Otto points out that no one saw them on the road approaching the town. He accuses them of hiding in the woods and waiting to rob, or even assassinate, the Baron as he passed.

At the local inn, Han’s mother and sister, Frau Tod and Greta, are rushed off their feet serving customers. Greta says there was an emergency council meeting this morning during which the burgomaster claimed the Beast of Orlok had returned. Her mother refuses to listen to such gossip. She knows Otto Pausbacken is nothing more than a scaremongering toad and likes nothing more than to keep the town in a permanent state of panic as it allows him to hold on to his power. She has some good news for Greta - her brother Hans is returning home this afternoon and will be spending the Christmas holidays with them.

The Doctor shows the burgomaster the letter he found from Grand Duke Albrecht, claiming it gives him full authorisation to take over the investigation. Adding that he outranks everyone here, including Otto, he insists that he and his friends be released from the cell so they can begin their search for the Beast. The Doctor asks Hans to apply his knowledge of philosophy to decide where they should begin the investigation and the young man suggests they visit Baron Teufel and ask him what he saw. At first Otto refuses to let them question the Baron, but the Doctor threatens to report him to the Grand Duke unless he complies. The Doctor also remembers that the broken walking stick was covered in clay when they found it, and as there isn’t any clay in the Black Forest, it must have come from whatever attacked the coach. He asks Lucie and Hans to fetch the spectroscope from the TARDIS so they can use it to follow the creature’s spoor. They agree to meet back at the inn run by Hans’s mother in two hours‘ time.

The two figures who were watching the Doctor, Lucie and Hans earlier come across the TARDIS where it landed in the forest. Appearing to recognise it for what it is, the first man orders Wolf to load it onto their caravan. He asks his companion if he put up the posters in town as requested and Wolf grunts to confirm that he did. The trap is now set and all they have to do is wait for their two targets to take the bait. After all, who could resist having their fortune told by the world famous Mystic Traveller?

At the inn, Greta excitedly tells her mother about the Mystic Traveller, palmist to nine royal families and three Popes, according to the posters. The group has apparently pitched up camp close to the edge of town and Greta is keen to go right now so she can be back in time for when her brother Hans arrives. Frau Tod assures her all fortune tellers are fakes and says Greta’s mind is already too cluttered with rubbish.

The burgomaster is sent to collect the broken walking stick to aid with the investigation, but as he rummages through the collection of objects taken from the scene of the accident, he stumbles across the sonic screwdriver. Believing it to be a gift to the Doctor from the Grand Duke, Otto pockets the device.

At Castle Orlok, the Doctor accepts a glass of wine from Baron Teufel and notes that his host seems unfamiliar with the brand. The Baron appears to be fully recovered from his ordeal and he thanks the Doctor for saving his life. Unfortunately not only can he not recall anything of the accident, he says he can’t remember a single moment of his life from before this morning - although from what he’s heard, he hasn’t been a very nice man, so he regards his lack of memory to be a blessing.

The burgomaster visits the inn and bangs impatiently on the door. As they’re not due to open for several hours, Frau Tod responds grumpily and demands to know what he wants. Discovering the Doctor hasn’t returned yet, he leaves behind the walking stick and tells her he has better things to do than get involved with wild goose chases. As he turns to go, he adds that he also has something else belonging to the Doctor but he’ll need to collect it personally. Watching from a hiding place, Lucie assumes the burgomaster was referring to the TARDIS as it was missing when she and Hans went to find it earlier. She learns that Otto has a reputation for petty revenge, so taking the Doctor’s possessions for no good reason is entirely in character. Hans points out that without the equipment from the TARDIS they’ll never be able to track down the Beast, but Frau Tod insists the real Beast is inside Castle Orlok.

In the Castle, Baron Teufel shows the Doctor to his secret laboratory hidden deep in the cellars, complete with electro-static generators, bi-electric field dampeners and even an en suite bubbling tar pit. The Baron has no recollection of its purpose, but it seems he was dabbling in science - and the equipment is still working after all these years. The Doctor is impressed as it’s state-of-the-art technology for 1827. Teufel passes him a notebook which suggests he was working on creating life itself.

Frau Tod once again rebukes her son for saving Baron Teufel’s life, insisting the man is pure evil. Hans suggests he may have changed in 20 years, but his mother refuses to listen to any arguments and says if anything he’s probably just become more cunning. Lucie points out that Teufel didn’t seem particularly evil to her when he looked at her, but Frau Tod reacts instantly to her words. She prepares to leave for Castle Orlok and pleads with her children not to follow her. As soon as she’s gone, Lucie decides the Doctor must be in trouble and plans to rescue him. She encourages Hans to go with her, pointing out that they can sneak into the Castle through the back while his mother is keeping the Baron busy at the front.

In the laboratory, the Doctor reads Baron Teufel’s notes. 20 years ago, the Baron lowered a cadaver into a vat of amniotic fluid and charged it with electricity, then watched as it started to come to life. The Doctor tells him to stop acting the innocent. He accuses Teufel of grave robbing, mutilation and even murder as the notes suggest the experiments worked best when fresh body parts were used. He doesn’t believe the Baron’s claims not to remember anything and says this room must have been like a charnel house. He believes Teufel has come back to pick up where he left off and accuses him of faking the attack on the road in order to give himself the perfect alibi. When mutilated bodies start turning up again, everyone’s going to blame the Beast of Orlok, rather than him. The Baron becomes hostile and says he’d expected more from a Time Lord. The Doctor demands to know how Teufel knew he was a Time Lord and the Baron explains that he recognised the sonic screwdriver. The man reveals that the real Baron Teufel is dead…and the Doctor will soon be joining him!

Lucie is disappointed to discover that the only back entrance into the Castle is via a sewage outlet. Hans explains that it’s the only way to get inside without being observed and says that he and Greta used to play here as children. One day their puppy chased a rat through the grating and was discovered a day later in the Castle storerooms. They manage to remove a grating and enter the building. They move down a dark tunnel, avoiding the rats as best they can, until they stop in their tracks when they hear a load roar coming from the darkness ahead…

A huge creature emerges from the shadows in the tunnel and moves towards Lucie and Hans. They flee for their lives, but the monster is soon gaining on them. Hans spots a side tunnel up ahead which they hope will be too narrow for the creature to enter, but this doesn’t stop the beast from trying and it starts ripping away at the brickwork, piece by piece. They race on, but find themselves trapped in a dead end. Lucie is sure the tunnel must lead somewhere or else there’d have been no point in digging it, but Hans says it’s an overflow channel and they can see water disappearing into a sink-hole. He apologises to her for leading them both into a trap.

The Doctor is hanging by his fingertips over the edge of the pit of boiling bitumen. General Zoff taunts him for just prolonging the inevitable, then he lashes out with a heavy metal chain. Suddenly everything goes quiet and the Doctor hears the sound of Zoff’s body falling to the floor. The chain appears over the edge and Frau Tod’s voice calls out for him to grab hold of it. She helps him climb back up to safety, then introduces herself. The Doctor notices Zoff is out cold and Frau Tod reassures him that his friend Lucie is also safe and is back at the inn with her son and daughter.

Hans and Lucie start throwing rocks at the Beast, but they have no effect and just bounce off it. Suddenly Lucie gets swept away in the torrent of water flowing through the tunnel. Hans reaches out to grab her, but it’s too late and she disappears through the sink-hole. Hans jumps into the hole after Lucie and eventually they both emerge at the end of a very long tunnel. Lucie is unconscious and Hans tries to revive her, but she doesn’t react to any of the life-saving techniques he’s been taught. Eventually he gives up and begins to cry…but then suddenly she begins to cough and slowly returns to normal.

At the camp outside the town, Greta visits the tent of the Mystic Traveller and is invited to take a seat. The mysterious man from the forest moves to take her hand, but he seems confused when she tries to place a coin in his palm. She explains that this is a tradition with gypsies, but he tells her he’s not a gypsy. He says he’s going to pour some water onto her hand and tells her not to be afraid. He then reveals how the water forms strange pools in her hand like mercury. Greta says it’s always been like that and the girls used to tease her when she was at school. The Travellers asks her whether she has a brother…

Burgomaster Otto Pausbacken addresses the townsfolk and tells them death has returned to haunt them. After two decades of peace, their beloved home is yet again besieged by evil and the Beast of Orlok walks among them once more. He also shows the crowd a poster for the gypsy fortune teller and warns them this charlatan is plotting to deceive and defraud them…or possibly even worse. However, he says cause of their current woes is two new people who arrived in town this morning. The man and woman claim to have been sent by the Grand Duke himself, but Otto knows they’re lying as he’s received word that the real agent of the Duke was a man called Klaus Lügner. His body was found in the wreckage of the crashed coach - which means the Doctor and Lucie are impostors! He says the Beast is a trick conjured up by the Doctor and asks the crowd how many more people must die before his bloodlust is satisfied? He whips the mob up into a frenzy, then suggests they go to Castle Orlok so they can end their terror tonight…

As Frau Tod ties up the unconscious General Zoff, the Doctor asks her how she knew the Baron was an impostor. She tells him Lucie described the way he looked at her and she knows for certain that the real Teufel is blind because she was the one who blinded him! The Doctor is unfamiliar with the Radzera Planetary League, but assumes they’re some sort of military alliance as the Radzera System is always at war, with each planet trying to trounce its rivals. Every so often one of the planets teams up with a neighbour and tries to dominate the others, but then it will develop a new weapon and decide to try it out on its ally. The same pattern has repeated itself over and over for centuries. The Doctor recalls that General Zoff was here to find some “experimental units” which he guesses refers to some new military hardware. He also notes that Zoff suspected the Time Lords were tracking him, which means he must be dealing with outlawed technology, possibly biological or temporal. He suspects it’s most likely to be clones, cyborgs or genetic mutations. He also notes that Frau Tod has understood everything he’s been saying and hasn’t reacted to it with any surprise. Frau Tod reveals that she knows what these “experimental units” are…

Lucie is cold, wet and very muddy - but otherwise unharmed. She thanks Hans for jumping in after her and saving her life. She’s amazed when he tells her they were both underwater for ten minutes, so Hans has no option but to tell her the truth. Before he can do so, the Beast emerges from the water, having evidently followed them down the tunnel. Lucie and Hans get to their feet and run for their lives again…

The Mystic Traveller has revealed the truth to Greta. He says his real name is Judah and he and his men have travelled a considerable distance to find her and her brother, disguising themselves so as not to alarm them. He says she and Hans are unique and he created them both in a laboratory, but then he had to send them to this primitive world for their own safety. Unfortunately, there are others looking for them too and he believes General Zoff has made Castle Orlok his headquarters. He orders his men to arm their impulse rifles and abandon anything that isn’t absolutely essential as they need to leave for the Castle immediately to rescue Hans.

Frau Tod explains that 20 years ago, a star fell in the forest near Orlok. The Beast was still abroad in those days, so none of the townsfolk would dare venture out after dark, but she was curious and went into the woods alone. She discovered the ‘star’ was made of metal. A door slid open and inside she found two babies, a boy and a girl. She knew they weren’t safe where they were, so she picked them up and carried them away - just as the metal ship exploded. She was knocked unconscious and when she recovered, she saw a man dressed in black and wearing a mask standing over her. In one hand he carried a bloodied blade and in the other was a man’s severed arm. She recognised his voice immediately as that of Baron Teufel. He demanded that she give him the children, but she refused to hand them over. She realised at that moment that Baron Teufel was the Beast of Orlok and it was he who’d been slaughtering and dismembering people, although for what purpose she couldn’t guess. As the evil man reached to grab the children from her, she picked up a burning branch and hit him in the face with it. The next day, the blinded Baron left Orlok and when the attacks ceased the stories of the Beast faded back into legend. She named the children Hans and Greta and brought them up as if they were her own, but she always knew that one day, someone from beyond the stars would come looking for them and take them from her.

The Doctor promises Tod that no one will take the children from her while he’s around. Just then, General Zoff taunts them and they realise that while they‘d been talking he‘d escaped from his bonds and armed himself. Tod wonders why the impostor looks so much like the real Baron Teufel and the Doctor suggests he’s using a metamorphiser. Criminals use them all the time to change their voices and appearances. Zoff points his molecular disruptor gun at them and warns that the effects can be extremely unpleasant. Tod refuses to let him get her children, but Zoff insists that he’s paid for them and if it wasn’t for the fact that their original owner Judah had a last minute crisis of conscience, he’d have them already by now. He activates a tracking device and announces that his Golem is closing in on the children…

Having escaped from the tunnels beneath the Castle, Hans and Lucie desperately try to keep a distance from the advancing Beast. They race into the forest and are relieved to see that the dense trees are slowing the creature down. They see lights up ahead and believe they must be quite close to the town by now - but suddenly they find themselves confronted by burgomaster Otto Pausbacken and an angry mob of torch-carrying villagers. Otto orders his men to seize the two youngsters…

The Doctor is horrified to learn that Zoff brought a Golem to Earth with him. He tells Tod that Golems are artificial lifeforms, but they’re outlawed by Article 12 of the Galactic Code. They’re the best soldiers in the Universe and they obey without question. They never give up and are made from virtually indestructible aluminosilicate. The Doctor suddenly realises this is where the clay on the walking stick must have come from - the Beast wasn’t covered in clay, it’s actually made of it!

In the forest, Otto demands that his prisoners tell him where he can find the Doctor. Lucie knows the Beast isn’t far behind them and warns the lynch mob they’re in great danger. Frustrated, Otto slaps Lucie viciously across the face - but then they all hear the terrible roar of the creature coming from the darkness around them. The villagers start to panic, but Otto assures them all they’re perfectly safe as he has a device that can control the Beast. He produces the Doctor’s sonic screwdriver just as the trees next to them are literally ripped from the ground by the terrifying monster. Otto stands before the Beast and tells it he’s brought a sacrifice for it. As he prepares to push Lucie forward, the creature grabs hold of him and lifts him high into the air - then it rips the burgomaster’s head clean from his body!

Zoff’s tracking device shows that the Golem has found its target. Frau Tod pleads with him to call off the creature, but he tells her it’s too late and he couldn’t even if he wanted to. The Doctor confirms that once an order is given to a Golem it can’t be countermanded until the mission is accomplished - even if the person giving the order dies. Golems are unthinking, unfeeling killing machines and that’s why they’re illegal in every civilised system from here to Andromeda. They’re the ideal foot soldier because they obey every order and never answer back. Zoff reveals that the experimental units are a new breed of Golems, ones that are intelligent, articulate and capable of learning and adapting to new situations. They’ve been fashioned in their creators’ own image so they can integrate perfectly into society. Tod is horrified to realise that Hans and Greta are the first of this new race and that Zoff intends to create an army of such creatures.

Judah and his men arrive at the scene of carnage in the forest. Three people were killed and Judah is furious with Zoff for bringing a full-size combat Golem to an inhabited planet. Greta asks if there’s any sign of her brother or Lucie, but the only thing they find is the Doctor’s sonic screwdriver. Unfortunately it looks like the Golem has captured them…

The Golem bursts through the doors of Castle Orlok and delivers its two prisoners, Hans and Lucie, to its controller. Frau Tod races over to be with her son. Zoff is delighted and believes his victory is complete, but it soon becomes apparent from Lucie‘s behaviour that she‘s not the person he was expecting. Zoff is confused as the Golem can’t make mistakes and was programmed to destroy anything that wasn’t made from aluminosilicates. The Doctor points out that Lucie and Hans are both covered entirely in mud and wonders what they could have been up to. Zoff orders the Golem to dispose of the Doctor and Lucie and the huge creatures strides towards them…

The Doctor hands Lucie one end of the chain and tells her he plans to use it as a bola, a South American throwing weapon. If they can wrap it around the Golem’s legs, they might be able to immobilise it. Lucie has a better idea and suggests they lure the monster towards the tar pit where they can trip it up and push it over the edge. Zoff realises what they’re trying to do and shouts out a warning to the Golem, but he’s forgotten that once an order’s been given it can’t be countermanded. Frau Tod mocks him and he angrily strikes her down, which infuriates Hans. The Doctor and Lucie are successful and the Golem tips over and drops down into the boiling tar, where is swiftly disappears from sight.

Zoff bitterly congratulates them and says he’s never seen a Golem defeated in hand-to-hand combat before. However, the odds are still in his favour as he’s used the distraction to attack Hans, shaking up the young man’s molecules and leaving him unconscious on the floor. He moves to kill Frau Tod, but before he can do so, Judah and his men burst through the shattered door and shoot Zoff down. Judah orders Wolf and the others to secure the General and take Hans back to his caravan to recover. Greta races in and hugs a relieved Frau Tod. Judah introduces himself to the Doctor and Lucie and reassures Hans’s mother that her ’son’ will be fine. Tod and Greta decide to go with him so they can be there when he wakes up. Judah says he’s located Zoff’s spacecraft and will be sending him home as soon as they’ve left the Solar System. Lucie is surprised they’re not planning to lock him up after everything he’s done, but Judah thinks the humiliation and loss of rank will be punishment enough.

Just as they’re about to leave, they hear a strange ominous bubbling coming from the tar pit. Suddenly the Golem bursts out from the boiling liquid and climbs back up to the laboratory floor. The Doctor, Lucie and Judah take cover as the enormous creature strides towards them, still intent on completing its mission. It rampages across the laboratory, killing Judah and then turning its attention on the others. The Doctor insists that Lucie leave the building and get Wolf and the others as the soldiers are their only hope of defeating the Golem. Reluctantly she races out, leaving the Doctor behind to defend himself alone. As the creature moves towards him, the Doctor realises it’s literally starting to crack apart, like a big lump of clay inside a kiln…

Lucie runs outside the Castle and calls for Wolf, but it’s Frau Tod she encounters first. Lucie quickly explains that the Golem has come back to life again and killed Judah. Before anyone can react, there’s an enormous explosion and everyone drops to the floor as the air is filled with falling debris. Lucie tries to get back inside the building, but Tod holds her back, pointing out that the entire Castle has collapsed. Even if the Doctor is still alive down in the laboratory, there’s nothing anyone can do now.

Buried underneath piles of rubble several floors below ground level, the Doctor bemoans the fact that he’s about to die just before reaching his millennium. Just then, he hears the sound of the TARDIS engines and his ship materialises a few feet away from him. The door opens and he’s amazed to see Lucie emerge - only for her to rebuke him for giving her dodgy instructions. The big red button he told her about earlier turns out to be a green switch!