While Victoria is off studying graphology, the Time Lords send the Second Doctor and Jamie to Space Station Chimera in the Third Zone, where some of the region's greatest minds are working on pure scientific research. The Doctor is upset that the Time Lords have fitted the TARDIS with a remote control and given him a recall disc, but prepares nonetheless to slip in quietly and speak with his old friend Joinson Dastari, Head of Projects. The TARDIS materializes in the kitchens, where the Androgum chef Shockeye assumes that Jamie is a food animal brought by the Doctor as a gift for Dastari. The Doctor ushers Jamie out of the kitchens, and as they go the TARDIS dematerializes by itself. The station's chatelaine, Chessene, is forced to change her plans, as she'd intended to give the TARDIS to her ally Group Marshal Stike. Stike is on his way and Shockeye has slipped a calgesic into the scientists' last meal. Chessene goes to the monitoring station, kills the officer on duty and opens the docking bays to approaching Sontaran battle cruisers...

The Doctor and Jamie meet with Dastari, who claims to be disappointed by the Time Lords' refusal to participate in Chimera due to their policy of non-intervention. This policy explains the Doctor's presence; he's been sent to request that the scientists Kartz and Reimer stop their experiments into time travel, and he was chosen because of his official status as an exile -- they can always deny having sent him, thus seeming to hew to their official policy. The conversation is interrupted when Chessene checks in to see whether Dastari's guests require refreshments, and the Doctor is appalled when he realizes that Chessene is an Androgum whom Dastari has technologically augmented up to the mental level of a mega-genius. Dastari insists that the future of the Third Zone lies in the Androgums, if he can raise their fierce energy to a higher level of consciousness; but the Doctor believes that Chessene remains a savage Androgum by nature and Dastari has given great power to someone incapable of handling it.

The Doctor returns to his original point, warning Dastari that Kartz and Reimer's experiments have already caused dangerous ripples in the space-time continuum, but Dastari refuses to bow to the arrogant demands of the Time Lords and suggests that in fact they simply wish to protect their own secrets...isn't that why they removed the Doctor's TARDIS from the station before Kartz and Reimer could examine it? The argument seems to exhaust Dastari, who slumps at his desk... but the Doctor realizes that Dastari has been drugged, and he and Jamie hear gunfire in the corridors. A scientist rushing in to warn Dastari of the danger is shot down in the doorway. The Doctor orders Jamie to flee, and as he does so the Doctor is held at gunpoint by one of the invaders...

Somewhere else altogether, the Sixth Doctor and Peri are fishing in an alien river, but the Doctor gives up when he only lands a tiny fish the size of his hand. He returns to the TARDIS to find somewhere else to relax, telling Peri he hasn't felt himself lately... but before he can explain he collapses on the floor and goes into convulsions.

Jamie watches in horror from hiding as the invaders increase power to a glass tube through which electrical discharges are crackling through the agonised Second Doctor. Shockeye finds and nearly captures Jamie, but he's distracted when Chessene arrives looking for him and Jamie takes the opportunity to flee. Shockeye, upset at losing this catch, requests that Chessene conduct the rest of the operation on Earth, so he'll have the opportunity to capture and eat one of these human beasts. He's furious when Chessene concedes to his request with amused contempt, and accuses her of forgetting the history of her clan the Franzine Grig and the law of the Androgums, which praises the gratification of pleasure. But Chessene has found new pleasures and has had a vision of the future...

The Sixth Doctor pulls himself together, confusing Peri with his stream-of-consciousness ramblings as he tries to recall what happened to him. All he remembers is being put to death, but he can't have been executed before or else he wouldn't be here now, would he? Perhaps his regeneration hasn't stabilised yet and he suffered a subconscious timeslip. Peri suggests getting medical treatment, and the Doctor leafs through his collection of business cards. For some reason the name Joinson Dastari catches his attention, and he sets off for Chimera in the TARDIS.

The station has been long since deserted by the time the Doctor and Peri arrive; something animalistic slathers through the infrastructure, and the air reeks of decaying food and death. The Doctor and Peri head out into the corridors and find the aftermath of a fierce battle; the walls have been pockmarked by laser fire and a coat drenched with blood lies on the floor. The Doctor is furious and determined to know who sanctioned this slaughter, and is startled when the computer comes to life and informs him that their work threatened the Time Lords. When the Doctor refuses to go, the computer switches to defense alert, and seals off and begins depressurizing the corridor. Peri faints from lack of oxygen, but the Doctor finds a failsafe hydraulic pump, opens a nearby door and carries Peri to safety.

The Doctor and Peri hide in Dastari's office, since the computer has been tracking them by the heat of their feet and the floor here is made of cork insulation and carpet. The Doctor, determined to find out what's behind the atrocity he's witnessed here, searches Dastari's desk and finds his day journal. He is appalled to find that Dastari's last entry expresses concern that the Time Lords will forcibly intervene to stop Kartz and Reimer's time experiments since Dastari had refused to call a halt to them. Peri suggests that someone may be framing the Time Lords for the massacre, and the Doctor agrees and is determined to find out who. The computer begins to turn up the ambient temperature, preparing to roast the Doctor and Peri to death, but the Doctor snaps a wire free from a modern art sculpture on Dastari's desk and uses it to short-circuit the door lock and escape. He intends to get to computer control and deactivate the defense system, and in order to do so intends to pass through the infrastructure of the station, where the computer will be unable to detect them.

Chessene, Shockeye, and the Sontaran officer Varl have landed on Earth near the hacienda of the elderly Dona Arana. Dona Arana has just finished praying to a statue of the Virgin Mary when Shockeye finds her and snaps her neck. He's disappointed in the thin, gristly body, and Chessene finds little more of use in Dona Arana's mind; she was mainly concerned with her religion. All Chessene learns is that this planet is grossly overpopulated, and that they're in a region known as Andalusia, four kilometres from the city of Seville. She's amused when Shockeye eagerly inquires after the eating there, and Shockeye, affronted, reminds her once again not to forget her origins as an Androgum.

The Doctor and Peri enter the infrastructure through an access shaft in the kitchens, and head for computer control. On the way, Peri thinks she hears something following her, but the Doctor is initially too involved in explaining the function of the fluidic streams to pay attention to her (although he too hears something moments later). Eventually they reach the computer control, and the Doctor prepares to disarm it; it's a type 49 system, colour-coded and booby-trapped, and the Doctor proceeds carefully while trying to remember what blue stands for. Peri, bored, wanders off.

Shockeye and Varl disagree whether Chessene or Stike leads this operation; in any case, Stike is on his way in, with his ship on full mufflers. What none of them know is that two locals are trespassing on the hacienda's grounds. Expatriate English actor Oscar Botcherby is taking his Andalusian girlfriend Anita moth-hunting, and as Botcherby proudly shows off his moth-hunting equipment -- net, lantern, cyanide jar -- he and Anita hear a roaring noise and duck as something large passes by overhead. Assuming that a private plane has crashed, they go to investigate, and Oscar catches a glimpse in the distance of two figures carrying a third, unconscious man towards the hacienda. Anita points out that Dona Arana will be unable to help and has no telephone, and despite Oscar's reluctance to get involved he follows Anita to the hacienda to offer assistance.

Peri knocks her attacker out and pulls the Doctor free from the wires. As he recovers, he explains that he closed off his respiratory passages in order to survive. He's surprised to see that Peri's attacker was human, and even more startled to recognize him as Jamie. Jamie recovers and begins to panic, but the Doctor uses acupuncture needles to temporarily paralyse him while his body and mind recover from his ordeal. Jamie begins to babble about the Doctor's death, and the Doctor, recalling his earlier mindslip, hypnotises Jamie and questions him. He recognizes Jamie's description of the invaders as Sontarans, but isn't sure what to make of his insistence that the Sontarans killed the Doctor. He orders Jamie to sleep and relax; when he awakens he'll be fully recovered.

The Doctor and Peri enter the main computer room, while the Doctor theorizes that the Sontarans attacked the station to keep the Third Zoners from growing too powerful and allying themselves with the Rutans, and forced Dastari to write the last entry implicating the Time Lords in order to drive a wedge between them and the Third Zoners. As Peri examines herself in a mirror on the far wall, the Doctor briefly outlines the nature of the Sontaran-Rutan war and searches the computer records for the Kartz-Reimer experiments. What he finds appalls him -- it's entirely possible that his previous incarnation materialized on the station during a time experiment and was caught up in an embolism outside the normal flow of Time, in which case it would be possible for him to have been killed earlier and yet still be alive now. In which case the holistic fabric of Time itself has begun to collapse from the weight of paradox, and within a very few centuries the Universe will no longer exist...

Peri, unable to understand the scale of the disaster, heads off to see whether Jamie's all right. The Doctor bleakly ponders the prospect of eternal nothingness, but as he does so he happens to glance up and sees Peri trapped in a glass tube while electrical discharges crackle through her body. Trying to find the release switch, the Doctor presses a certain control, and suddenly it's Dastari trapped in the tube. He continues to press buttons and sees the tube's occupant change to his own previous incarnation, Peri again, Dastari again, and then his own current incarnation. When Peri returns with the recovering Jamie, the Doctor jubilantly explains that his theory about the embolism was wrong; the Sontarans faked his death to forestall an investigation into his kidnapping, but left the animator switched on by accident so it recorded the bodyprints of everyone who looked into the mirror in this room. The Sontarans must be forcing Dastari to conduct an operation to isolate the symbiotic nuclei within the Doctor's body, the link which allows a Time Lord to control their TARDISes. With this secret, the Sontarans could achieve time-travel.

The Doctor, hoping to connect with his previous self's mind as before and thus find out where he's being held, puts himself into a trance. The Second Doctor has been taken to the hacienda's wine cellars, where Chessene and Dastari administer an injection to counter the effect of the drugs which kept him unconscious during his journey to Earth. He recovers temporarily as a bell rings in the distance. Back on Camera, the Sixth Doctor snaps out of his trance, confused, with the sound of the bell ringing in his memory, reminding him for some reason of getting his hair cut.

Varl and Shockeye bring Dastari's operating equipment into the cellars while Stike cloaks the Sontaran ship to avoid detection. Dastari is upset that Chessene chose such a heavily populated planet for the experiment, but Chessene explains that Stike wished to set up close to his forces in the Madillon Cluster, and that she decided to indulge Shockeye's wish to taste the flesh of a human animal -- partly because as an Androgum she shares his desires, and partly to ease the shock of betrayal Shockeye will feel when she reveals the full extent of her plans. Dastari urges her not to let herself be trapped by the chains of tradition and is repulsed when Shockeye catches, kills and eats a rat, sampling the raw ingredients of this new environment. The Second Doctor slowly recovers, and is appalled to realize that Dastari anaesthetized him with siralanomode, a drug which affects the memory. When Stike and Varl enter the cellar he remembers the attack on the space station, and Stike casually informs him that since Sontarans take no prisoners his companion Jamie will be long since dead. Dastari and Shockeye are forced to restrain the struggling Doctor to the operating table when he lashes out angrily at the Sontarans.

The Sixth Doctor finally recognizes the sound of the bell as that of the Santa Maria, the largest of the bells in the Cathedral of Seville. The echoes and after-resonance indicate that he's being held in a dungeon about three miles away. With Jamie and Peri accompanying him, he pilots the TARDIS into the grounds of the hacienda, right into Oscar and Anita's path. Oscar has already commented on the lack of wreckage and suggested that they leave to summon official help; he's only going along because Anita insists upon helping immediately, and has suggested that the publicity of a rescue might convince the British Consulate to book Oscar on a forthcoming tour. When they spot the Doctor, Jamie and Peri emerging from the TARDIS, Oscar notes the police insignia on the box and assumes that it's an Interpol outpost. He reports the "plane crash" to the Doctor, who is intrigued and asks for directions to the hacienda. Anita offers to lead them, and Oscar summons up his courage and goes along as well.

The Second Doctor watches as Dastari sets up the prototype Kartz-Reimer module, in which several Androgums were successfully transported into the Time Vortex. Unfortunately they never returned, because successful time travel requires a molecular stabilisation link of some kind -- and it was Chessene who guessed that the Time Lords possessed a symbiotic link with their TARDISes. The Doctor realizes that Dastari is entirely infatuated with his creation, and he's right; Dastari refuses to listen to anything said against Chessene, and ignores the Doctor's warnings that if he gives her time travel she'll release the savage Androgums upon the galaxy and Dastari will be responsible for catastrophe. Stike is growing impatient with the delays, as it's vital he be present to lead the attack on the Rutan forces in the Madillon Cluster, but Dastari points out that if they'd dismantled his operating theatre any earlier the occupants of the station would have been alerted to the fact that something was going on. Stike reluctantly helps to set up the operating theatre, and the Doctor tries to provoke him, claiming that Chessene has no intention of passing on the secret of time travel to the Sontarans, questioning Stike's honour and bravery, and challenging him to a duel. Stike, however, refuses to rise to the bait, knowing that they need the Doctor alive and that he would just try to escape if Stike released him to fight.

The Sixth Doctor scouts out around the hacienda while his friends wait nearby. He happens across the window to the kitchens, where Shockeye is showing Chessene some of the cookbooks he's found. Shockeye has come to conclude that the humans aren't as primitive as he'd believed. They have astonishingly advanced methods of food preparation, which they use on almost every animal on their planet; in fact, some are bred especially for table, penned in confined quarters and force-fed to fatten more readily. Shockeye by now is slavering for the taste of a human, which must be at the top of the planet's food chain, and Chessene agrees to find one before leaving Earth and to join him at table, as she's curious herself.

Oscar explains to Jamie and Peri that he's managing a small restaurant, Las Cadenas, for a friend whilst between roles. The Sixth Doctor returns and announces that the hacienda has been occupied by alien beings. Jamie recognizes the Doctor's description of Chessene, and the Doctor is appal- led when Jamie tells him of her augmentation, agreeing with his other self's assessment of the danger. He tells Peri to go to the hacienda to distract the occupants while he and Jamie try to break in and find out where he's being held, and Anita offers to show them a secret way into the cellars from the old icehouse. Peri goes to the hacienda and knocks on the front door, and Shockeye, who's comparing the late Don Arana's clothing to his own build, hears her. He looks out of the window to see a young, well-muscled, female human -- just what he's been waiting for...

Dastari administers an anaesthetic to the Second Doctor to paralyse his motor cells; unfortunately, the operation requires him to be conscious while Dastari dissects him. The Doctor is soon unable to move, and as Stike and Varl watch impatiently, Dastari prepares to cut open the Doctor's skull and detach the occipital lobe. But Peri calls out from upstairs and the operation is put on hold while Chessene investigates. Peri claims to represent a tourist company looking for accommodations for American students, but Chessene scans her mind and realizes the uppermost thoughts are of the Doctor. She sends Shockeye to the cellars to fetch Dastari and bring the Doctor through the hall, to see whether Peri gives herself away upon seeing him. If so Shockeye will have found his meal...

Anita leads the Doctor and Jamie to the icehouse, and the Doctor tells her to get off the estate to safety as fast as she and Oscar can run. In the cellars, Stike is holding Dastari at gunpoint, ordering him to continue the operation. Dastari points out that if Stike kills him he'll lose all hope of isolating the Time Lords' symbiotic nuclei, and Stike angrily allows him to take the Doctor away -- but warns him that if the operation isn't completed successfully by the end of the day he'll kill everyone and leave anyway. The Sixth Doctor and Jamie arrive just in time to see Shockeye and Dastari bundle the Second Doctor into a wheelchair and cart him off. Realizing he has no hope of surviving a fight with an Androgum such as Shockeye, the Doctor decides to take the opportunity to study the equipment set up here, and finds the Kartz-Reimer module. It's almost functional, but, as the Doctor explains to Jamie, it needs the symbiotic print of the "Rassilon Imprimature" in order to function properly. Once the Doctor or any other Time Lord has used the machine, their symbiotic print will be absorbed into the briode-nebuliser and then anyone will be able to use the Kartz-Reimer module to time-travel. And Stike and Varl emerge from the shadows, having heard everything...

Shockeye knocks Peri unconscious and takes her back to the hacienda.

Stike, unaware of the Doctor's true identity, assumes he's simply another Time Lord come to investigate. He sends Varl to tell Chessene what's happened, and then holds Jamie at gunpoint and forces the Doctor to prime the Kartz-Reimer module. The Doctor does so, and tells Stike that the module is now a fully-functional time machine which anybody can use. He distracts Stike for a moment and Jamie plunges his dirk into Stike's kneecap and escapes. Varl arrives with Chessene and Dastari, and they pursue the fleeing Doctor and Jamie to the icehouse but lose track of them. Chessene and Dastari return to the hacienda to plan their next move, leaving Stike and Varl to search for the fugitives. But Stike has other plans; now that the time module is fully operational he has no need of the others...

The Doctor and Jamie have returned to the hacienda, where they find the Second Doctor recovering from his paralysis but strapped into his wheelchair. Before they can free him, Shockeye arrives, carrying Peri through to the kitchens; the Sixth Doctor and Jamie hide, but before they can emerge Chessene and Dastari arrive, discussing their next move. Now that the Time Lords have located them there is no time to carry out a slow and careful operation on the Doctor, but Chessene has a contingency plan. If Dastari uses genetic material from Shockeye he can transform the Second Doctor into an Androgum hybrid with the symbiotic nuclei of a Time Lord, and he can act as Chessene's consort. This will require two operations; one to implant the genetic material, and a second to stabilise the transfusion. Chessene fetches Shockeye, interrupting him just as he was about to begin trimming the meat from Peri; the Second Doctor tries to warn him what Chessene intends to do, but Chessene shoots Shockeye, stunning him temporarily while Dastari carries out the operation.

Stike orders Varl to contact the Sontaran High Command, report the success of their mission, and then set their ship to self-destruct; Stike intends to kill the others and then depart for the Madillon Cluster in his time module. Meanwhile, the Sixth Doctor and Jamie rescue Peri and flee from the hacienda. The Doctor admits that he overheard Stike and Varl trying to creep up on him in the cellars and deliberately spoke about the Rassilon Imprimature so they could hear him. He's expecting the Sontarans to try to kill Dastari and Chessene and then escape in the Kartz-Reimer module; he stole the briode-nebuliser from it and if they try to use it they'll end up dead.

As the Second Doctor begins to transform into an Androgum, Chessene plans how to eliminate Stike and Varl. Dastari is uncomfortable at her casual discussion of killing, and is surprised to learn that she brought vials of coronic acid with her as a precaution. As they leave to set the trap, Shockeye recovers sooner than expected and tears himself free of the operating table, furious. But by this point the Doctor is largely an Androgum by genetic inheritance, and to Shockeye's delight, the Doctor is also familiar with the cuisine of this world. The Doctor offers to lead Shockeye to a local dining establishment to sample the local dishes, and Shockeye hurries off to fetch the clothing he was studying earlier.

The Sixth Doctor, Jamie and Peri watch from hiding as Dastari contacts Stike and Varl, telling them that Chessene spotted the other Time Lord entering the icehouse; if the Sontarans follow him through the passage they'll be able to trap him in the cellar. Stike and Varl enter the passage, but Chessene surprises them with coronic acid grenades, killing Varl and sending a wounded Stike running for cover. The Sixth Doctor sees Chessene leave the icehouse and realizes that his plan to trick the Sontarans has failed. As he ponders what to do next, he and his companions notice the Second Doctor and Shockeye leaving the hacienda together; puzzled, they follow the two, and are horrified when the Second Doctor waves down a passing truck and Shockeye snaps the driver's back with a single blow. The Second Doctor and Shockeye board the truck and set off for Seville, and the Sixth Doctor, Peri and Jamie set off in pursuit, the Doctor warning them that his former incarnation's Androgum inheritance will soon begin to affect him as well.

Dastari and Chessene return to the cellar to find the Doctor and Shockeye gone, and Chessene, realizing that they'll be hunting for food, draws on the Dona Arana's memories and sets off to Seville to search the restaurants. As they leave, Stike staggers out of hiding, his skin melting away from his face, and vows to return to destroy them both. He boards the Kartz-Reimer module and programs it to take him to safety, but due to the missing briode-nebuliser temporal energy discharges through the machine and he barely shuts it down in time. Mortally wounded, green pus pouring from his skin, he staggers out of the hacienda towards his spaceship... and reaches it just as it self-destructs.

The Sixth Doctor, Jamie and Peri find the truck abandoned in the streets of Seville and set off searching the streets for the Second Doctor and Shockeye. Peri takes the opportunity to ask how the two Doctors could cross paths, and the Sixth Doctor points out that he travels around so much it's almost inevitable. They see Chessene and Dastari searching the streets, and the Doctor realizes that they've narrowed their search down to the restaurants -- an excellent idea which should have occurred to him as well. He's distracted when he sees an alley cat wandering the streets, and dreamily begins listing the many ways in which a cat can be cooked, broiled, baked... but he snaps out of it and heads off, determined to find his former self before he becomes an Androgum forever.

The Second Doctor and Shockeye find Las Cadenas, the restaurant managed by Oscar Botcherby. Oscar bravely attempts to ignore his customers' eccentricities and allows them to eat over a dozen servings apiece before inquiring how they intend to pay. Shockeye hands over a twelve narg note, but Oscar continues to insist upon a more acceptable method of payment. As the Second Doctor passes out face-down in his meal, Shockeye, irritated by Oscar's continuing to bother him while he's trying to digest his food, stabs Oscar in the chest with his dinner knife and leaves the restaurant as Anita vainly tries to staunch the flow of blood. The Sixth Doctor, Peri and Jamie arrive moments too late, and Oscar dies as theatrically as he can manage. The Second Doctor's body rejects the Androgum genetic transfusion and returns to normal, and the Sixth Doctor drags him out of the restaurant as Anita mourns over Oscar's body. Outside, however, the Doctors and their companions are captured by Dastari and Chessene.

Shockeye arrives back at the hacienda first and greets the others with news of Stike's death. Chessene and Dastari take their prisoners to the cellars, where they find that the Kartz-Reimer module has been tampered with. The Sixth Doctor admits what happened and hands over the primed briode-nebuliser, and Dastari tests it by forcing Peri to enter the module and travel a few seconds into the future. The module works perfectly, but Chessene still doesn't trust the Doctors and has them and their companions chained up. Shockeye takes Jamie to the kitchens to trim and cook him. Dastari, clearly uncomfortable about what's happening, leaves the keys to the Doctors' manacles on a table just out of their reach. As soon as they're alone, the Sixth Doctor admits that he sabotaged the briodenebuliser, paring the interface but leaving a thin membrane so it would work for one test. Peri pushes the wheelchair over to the Sixth Doctor, who uses it to lever up the table and knock the keys onto the floor where he can reach them. He unlocks himself, but then hears Jamie screaming from upstairs, and leaves the keys with the Second Doctor while he goes to rescue his former companion.

Dastari watches in disgust as Shockeye electronically tenderizes Jamie, assuring the scientist that primitive creatures such as humans don't feel pain. Chessene bursts in, furious, having seen the Sixth Doctor escaping, and orders Dastari and Shockeye to find and kill him; Dastari is reluctant to kill a Time Lord, but there's no reasoning with Chessene at this point. The Sixth Doctor, hiding nearby, waits until they've left the kitchens and then breaks in and cuts the unconscious Jamie free from his restraints, but he is then confronted by Shockeye, who'd guessed that he would return for his companion. Shockeye slices open the Doctor's leg with a knife, and pursues the bleeding Doctor out into the grounds of the estate. Chessene, seeing the pool of blood on the hacienda steps, can't resist the smell, and as Dastari watches from a distance, she falls to the ground and laps up the blood, smearing it on her face like an animal. Repulsed, Dastari goes to the cellar, where he catches the Second Doctor and Peri trying to escape...

Trying to shake off Shockeye's pursuit, the Sixth Doctor stumbles and falls near Oscar's abandoned moth-catching equipment -- complete with net, thermos of water, and cyanide jar. With Shockeye only moments behind, the Doctor tips the cyanide crystals into a handkerchief and dips it in water. When Shockeye catches up with him, the Doctor throws the net over his face and slaps the cyanide-soaked handkerchief over his mouth and nose. Shockeye struggles briefly but quickly dies.