Episode One : THE CANNIBAL FLOWER

The TARDIS is pulled out of "free float" by a signal from a dead world, and materializes near a magnificent crystal building. Barbara senses something evil about the building, but the curious Doctor hovers over the building to investigate further. Before he can react, the roof of the building opens like a flower, and the TARDIS is pulled inside. The Doctor is unable to dematerialize, as something has begun to drain away the TARDIS' power. Ian and Susan leave the TARDIS to explore, and find a sumptuous feast laid out in a dining hall -- but no sign of any inhabitants. Ian stops Susan from eating the food, but samples a bit himself with no apparent ill effects.

The Doctor is unable to prevent the building from draining away the TARDIS' power, but notes that the signal which lured them to the planet is still transmitting although they've clearly arrived already. He is eventually forced to activate the emergency systems, but they too are drained, and the TARDIS falls lifeless. Have they been drawn into a cannibal building, which draws the life from other machines like a flower which traps insects?

Susan suggests that the building could be an automatic way-station, but Ian isn't convinced by her suggestion. In any case, he finds something worrying about a machine calling another machine to itself, with no sentient life involved at any point. He finds a set of buttons set into one of the chairs in the dining hall, and when he presses one, the alcoves in a nearby hallway swing around to reveal rows of deactivated robots. The Doctor and Barbara join Ian and Susan outside, but the Doctor is unable to explain what has happened. Trapped on the world, perhaps for the rest of their lives, they have no choice but to spring what may be a trap and eat the food which has been set out before them...

Episode Two : THE MOCKERY OF A MAN

The travellers finish their meal with no ill effects, and once he's had the chance to relax, the Doctor decides that he's allowed his human companions' fear of the unknown to affect him; after all, they have no reason to believe that an intelligence advanced enough to build such a complex would mean them harm. The travellers decide to press the next buttons on the chair to see what happens, and upon their doing so the dormant robots come to life. The robots greet the travellers as the "Masters of Luxor", and as they respond only to pre-programmed stimuli, the travellers are unable to convince them that they are not the robots' creators. The travellers are shown to guest rooms complete with baths and a change of clothing, but Barbara is still worried. The robots here behave like men -- or is it the other way around? The TARDIS has been drained of life; now what is to happen to its occupants?

Following their baths, the travellers are questioned by a Derivitron, a more advanced form of robot. It is also unable to go beyond the boundaries of its programming, and since it has not been programmed to believe in worlds other than Luxor and is unaware of any signal being sent from this planet, it cannot accept their explanation of how they came to be here. Instead, it concludes that they have come from Luxor to investigate why the living men do not return from this building -- and the travellers are horrified to learn that it's because the robots killed them when they refused to give up their lives.

The travellers are left alone and attempt to escape. They break out of the rooms easily enough, but realize too late that their escape is being guided. They eventually find themselves locked into a room overlooking a laboratory, where they are forced to watch as a terrified man is strapped into a chair next to the most perfectly humanoid robot of them all. The machine glows brightly, and the man writhes in agony before being vapourised. The Doctor and his companions are then brought before the robots' master, the Perfect One, who explains what is happening. The Masters of Luxor built robots to be their servants, and programmed them to act like slaves so they could feel superior to them. But when they developed the idea of the Perfect One, the robots perceived in the concept a creature who could set them free. Even the Perfect One is not truly alive, however, and what's worse, he is fully aware of it. Thus, he has been experimenting upon his creators to discover the secret of life -- and now the Doctor and his companions will become part of his experiments!

Episode Three : A LIGHT ON THE DEAD PLANET

The Doctor and his companions are given food and drink as the Perfect One explains what is to happen to them. Luxor is a world of scientific marvels and soulless lack of humanity, where female children who do not meet the exacting genetic standards of the society are killed at birth. This is a prison world, where "undesirables" used to be sent for experimentation. To ensure that the travellers do not attack him, the Perfect One warns them that he has connected a bomb to his own governing impulses; any attempt to damage him will destroy the entire building. Why should it survive beyond his own existence? The travellers realize too late that they have been drugged, and as they pass out they call the Perfect One "an evil creation of evil people", words which have no meaning to him. He will experiment upon the women, creators of life, first.

Susan and Barbara are taken to the laboratory, but recover and attempt to overpower their robot captors. In the confusion a power coil is damaged, and Susan and Barbara take the opportunity to escape. Ian and the Doctor are abandoned in a lift when their guards leave to deal with the emergency; unaware of what's happening, they theorize that the power loss is due to the building's inability to deal with the different quality of power drained from the TARDIS. Searching for a way out, they notice a light flashing in the world outside, in the same pattern as the signal which first lured them to this planet. The Doctor theorizes that the true Masters of Luxor have fled into the wilderness -- and since the light is only flashing when the building is powered down, that suggests that whoever is sending it doesn't want the Perfect One to know about it.

The Doctor and Ian break out of the lift shaft, and when the robots repair the damaged power coil the Perfect One orders that the building be sealed up behind them. Only the women are important; the men can be left to die on the planet's surface. Trapped outside, the Doctor and Ian locate the source of the mysterious signal -- a mausoleum in the centre of a cemetery, which may contain their only hope...

Episode Four : TABON OF LUXOR

The tombstones in the cemetery are carved with pious epitaphs, which are not at all what the Doctor and Ian were expecting from the soulless Masters of Luxor. Inside the mausoleum they find a hermetically sealed coffin, and once Ian breaks the seal the body inside comes to life. This is Tabon, the former Scientific Master of Luxor, and he's a shadow of the man he once was, wracked with guilt, grief and self-pity. He confesses to experimenting upon his fellow human beings to further his goal of creating the Perfect One; and even when he realized his madness and stopped his work, his own creations, the Derivitrons, completed it against his will. The Doctor convinces him to atone for his crimes by helping to rescue Susan and Barbara, and he admits that he's found a way back into the city which the Perfect One doesn't know about. Before leaving, Tabon insists that they pray for success to the God whose existence he once discounted, on the holy books he once burned.

Barbara and Susan have been recaptured and experimented upon, and withstand levels of power strong enough to kill the men of Luxor. The Perfect One, certain that the life force of the women will be powerful enough to pass into him, sends them back to the guest quarters to recover. Susan notices an electric eye monitoring their conversation, and smashes it; Barbara then fuses the wires leading from the eye to the wall. Now that they've started to fight back, they don't feel nearly as frightened.

Tabon leads the Doctor and Ian to the atomic magazines of the complex, but is horrified to learn that the Perfect One has reactivated them and set them to explode should he be damaged. Tabon slips back into despair, convinced that nothing can destroy the Perfect One; but the Doctor points out that since the Perfect One's mind is patterned upon Tabon's own, and that Tabon cowardly retreated from the complex to save his own life, the Perfect One will not do anything to risk his existence. They continue on to the atomic magazine, but once there, Tabon determines that he is unable to deactivate the self-destruct mechanism.

Barbara and Susan plant a wire by the door, planning to trip up the robots and escape. But instead, it's the Perfect One who arrives, intending to investigate their "destructive impulses" in person before he absorbs their life force. Before they can stop him from entering the room he trips over the wire and hits his head on the floor. In the atomic magazine, Tabon, Ian and the Doctor watch in horror as the readouts on the self-destruct circuit begin to rise...

Episode Five : AN INFINITY OF SURPRISES

The Perfect One recovers, and the atomic magazine returns to normal. Susan and Barbara, relieved by their narrow escape, demand to know what has become of their friends. When the Perfect One announces that they've escaped to their deaths, they are overwhelmed with relief and burst out laughing at his pomposity. Unable to understand their illogical reaction and fearing that their life force may be inferior, the Perfect One decides to analyse them further before draining their life force away. Barbara and Susan, realizing that the robots are unable to respond to anything outside their programmed parameters, attempt to confuse them further by singing hymns. Their plan backfires when the Perfect One adapts more quickly than they'd expected, works out that they're being deliberately confusing, and orders the robots to ignore their words and prepare them for immediate transference.

The Doctor and Tabon try to reverse the power drain and restore the TARDIS to life, while Ian searches for the surveillance room, hoping to keep an eye on the enemy. Instead he finds the Perfect One preparing Susan and Barbara for transference, and tries to stop him by claiming that Tabon told him the female life force was of an inferior quality. The Perfect One refuses to believe that Tabon is still alive; surely Tabon would love him as a father loves a son, and since he has not attempted to contact the Perfect One, this must mean that he is dead. When Ian claims that the Perfect One represents everything Tabon finds loathesome about science, the Perfect One tortures him, determined to make him admit he is lying.

Tabon and the Doctor enter the generator room, but the Doctor remembers too late to deactivate the electric eye. Realizing that the robots are on their way, Tabon nevertheless completes his work and then begs the Doctor to kill him before the Perfect One captures them. The Doctor refuses to do so; while they live, they're capable of springing an infinity of surprises upon mere robots. The robots report back to the Perfect One, who is stunned to learn that Tabon is alive after all. Determined to face his creator as a living being, the Perfect One straps Ian into the transference machinery, and, ignoring Barbara and Susan's pleas, switches on...

Episode Six : THE FLOWER BLOOMS

Susan frees herself from her restraints and interrupts the transference, and Ian threatens to attack the Perfect One to stop him from killing Susan. He and his friends have nothing to lose, since the Perfect One will kill them anyway if they can't stop him -- but now that the Perfect One knows Tabon is still alive, he has a reason not to wish his own destruction. The Perfect One waits out the stalemate, confident that Ian's determination will waver. But Ian, Barbara and Susan know that his confidence will be shattered when he meets his God, who is only a man.

Tabon and the Doctor are brought before the Perfect One, who is horrified when Tabon falls to his knees before him and begs him to release the others. They should be equals, Tabon should not beg before him... but the Perfect One now realizes that Tabon feels only shame when he sees his creation, and that the Perfect One will never be anything more than a mere machine. The Perfect One, unable to cope with his creator's rejection, orders the robots to destroy him, but Tabon countermands the order. The conflict of orders and the fact that they've effectively been told to destroy themselves sends the robots berzerk, and in the confusion, the Doctor and his companions try to retreat to the TARDIS.

The Perfect One, still seeking his own destruction, is struck and damaged by a berzerk Derivitron, and despite Ian and Tabon's attempt to prevent him from being damaged any further, he gets in the way of another robot which smashes his head in. As the Perfect One's brain insulation begins to leak out, Tabon holds the injury closed with his hands to give the others time to escape. He will sacrifice his life to save theirs; he hopes only that when the complex explodes, the Masters of Luxor will witness and learn from it. The Doctor and his companions retreat to the TARDIS, wait tensely for the power to return, and escape just in time. Moments later, the damage to the Perfect One becomes irrevocable, and the explosion of the atomic magazine destroys the entire planet.