When The Doctor and Sarah Jane Smith arrive on the planet Karn they discover a large number of crashed spaceships. They also spot a castle which they decide to investigate. Inside they discover it is occupied by Solon, a fanatical scientist, and his servant, Condo, a large man with a hook for a hand. Solon is delighted that he has humanoid visitors as he has decided that The Doctor's head is just what he needs to complete his work. He offers them hospitality but The Doctor and Sarah are unaware that the wine offered to them has been drugged. As they talk The Doctor realises who Solon is. The Doctor also recognises the clay bust, which Solon had been working on when they arrived, as that of the executed Time Lord criminal Morbius. But his realisation is too late as the drugged wine takes its affect and The Doctor falls into a deep sleep.
Sarah however, not liking the wine, is not affected by the drug. But on realising what has happened to The Doctor she plays along by pretending to fall asleep. Solon and Condo take the drugged Doctor off to Solon's laboratory where Solon's examination confirms that The Doctor is a Time Lord. Not realising that Sarah was only feigning unconsciousness, and has followed them, Solon and Condo leave The Doctor in the labratoty so as to fix the power generator. However, unbeknown to them both, and also to Sarah, as soon as they leave the laboratory the sleeping Doctor disappears into thin air. He has been transported to a nearby shrine occupied by the Sisterhood who believe The Doctor has been sent by the Time Lords to steal the last drops of Elixir produced by the dying Sacred Flame.
As Sarah sneaks into Solon's laboratory, left in partial darkness by the lack of lighting, to rescue The Doctor. She pulls aside some curtains around a bed, thinking that The Doctor must have been left there. She sees a humanoid figure lying on a raised platform and initially believes that this is The Doctor, but suddenly the power comes back on and she sees that it is in fact a hideous monster with no head and a huge claw in place of its right hand. This creature has been constructed by Solon using the remnants of spaceship crash victims to put together a new body for the still-living brain of Morbius. Sarah though is even more shocked to discover that this headless monster is alive when it lunges towards her.
On discovering that The Doctor has disappeared Solon concludes that it must be the work of the Sisterhood. Swearing revenge he and Condo go to get The Doctor's body back unaware that Sarah is following them. Meanwhile, having being kidnapped by the Sisterhood, The Doctor awakens and discovers that they plan to burn him at the stake. Solon and Condo however, interrupt the ceremony but Solon is unable to convince the Sisterhood to let him have The Doctor – or at least his head. However, Solon’s interruption allows a disguised Sarah to sneak up behind The Doctor and cut his bonds. But as The Doctor and Sarah try to slip away, they are spotted and Maren, the leader of the Sisterhood, hits Sarah with a blue bolt, from her ring, blinding her.
With Sarah seriously injured The Doctor has no choice but to return to Solon’s castle and ask for his help in curing Sarah. While Solon examines Sarah, The Doctor finds the headless body hidden behind the curtain. Solon then tricks The Doctor into believing that his companion's condition is permanent. The Doctor therefore decides to ask the Sisterhood to allow him to use some of the Elixir of Life to cure Sarah.
Still unable to see, and while left on her own, Sarah discovers Morbius when trying to locate the source of a guttural electronic voice that she can hear. On entering a secret laboratory Sarah locates a cylindrical tank in which Morbius's brain is suspended in bubbling green fluid. Morbius however, thinks that Sarah is one of the Sisterhood and rants that she has been sent to destroy him before his vengeance can begin...
Meanwhile The Doctor has managed to convince Maren that he is not here to steal their Elixir but is concerned that Solon is trying to resurrect Morbius. The Doctor also discovers that the Sacred Flame is dying. The Doctor is puzzled, as the Flame is fed by gases from deep within the planet and should last for millions of years and that if the gases are sealed in, the mountain could explode. Maren allows The Doctor to take a look at the Sacred Flame. Without any warning The Doctor uses a firework to clear its blocked chimney so restoring the Sacred Flame back to its former glory. Realising that The Doctor is telling the truth they agree to help him. They also inform him that Sarah’s eyesight will return on its own accord and that Solan was lying.
Back in the castle Morbius, on learning of The Doctor’s presence and thinking that the Time Lords have tracked him down, insists that he be transferred into an artificial brain casing Solon once constructed and then placed on the headless body straight away. Solon protests as there is no way to stop static electricity building up, which could result in severe pain and seizures that could drive Morbius mad. Morbius however, tells Solon that he will take this risk as he is desperate not to be caught again by the Time Lords.
|The Doctor is Drugged
After completing the operation Solon discovers that the Sisterhood have returned the apparently dead body of The Doctor. Left alone in the laboratory, with Morbius, the blind Sarah is unaware that Morbius is quickly recovering from the operation. As Morbius rises from the operating table he scares Sarah, whose eyesight has started to recover. She escapes and warns Solon that the creature is on the loose. As he heads off back to the laboratory Sarah spots The Doctor and is relieved to discover that he is not dead. However, when he explains that he is here to stop Solon, Sarah tells him it is too late.
Condo, on discovering that his missing arm has been used on Morbius, becomes angry with his master, Solon. Condo has also become infatuated with Sarah and so when Motbius goes on a rampage within the castle Condo is killed when he tries to stop the creature from killing Sarah. Despite the fact that Morbius is in intense pain, making him insane and very dangerous, The Doctor fails to persuade Solon to detach Morbius’ Brain so that it can be returned to the Time Lords. Trapped in the secret laboratory The Doctor releases cyanide fumes into the ventilation system and Solon is killed.
The cyanide however has no effect on Morbius and so The Doctor challenges him to a mind-bending contest – which Morbius accepts. However, this takes a heavy toll on both of them. As The Doctor collapses, Morbius stumbles out of the castle in a daze. The Sisterhood then arrive and hunt the crazed creature down. With lit torches they herd Morbius over a cliff where he falls to his death.
Meanwhile Ohica, one of the Sisterhood, enters the castle and goes down to the secret laboratory. There she finds Sarah cradling the dying Doctor. The Doctor is taken back to the Sisterhood’s shrine so that he can be given some of the Elixir of Life as it is only this that can save him. The Elixir is given to The Doctor, who revives almost immediately. After handing over some of the fireworks, so that the Sisterhood can use to keep the Sacred Flame alight, The Doctor and Sarah enter the TARDIS and it vanishes in a flash and a puff of smoke.