Original air dates 3 September – 24 September 1977.
Space shuttle in a field of rocks. Tense music. Shuttle flies through an unidentied space organism. “Contact is made”.
Doctor and Leela aboard the TARDIS in the main control room discuss where they have arrived.
Shuttle lands on Titan. Three figures in spacesuits emerge, go inside and shoot the three staff members. Revealed to be aliens with funny cheekbones who plan on killing everyone and making this a breeding area.
Supervisor calls distress call, which Doctor recieves, and goes to get him.
TARDIS flies through organism, and takes Doctor over. Leela is worried. Doctor is acting strange.
Supervisor sneaks back in to arrest invaders. Firefight. Supervisor hides, is locked in a room, oxygen turned off.
Doctor and Leela emerge, find dead alien. Investgate.
Doctor finds aliens, who mind-control him good. He’s going to begin the breeding from his nucleus, which sounds unpleasant. He’s also going to destroy the reject, meaning Leela and the Supervisor.
Leela finds Supervisor frozen in room, unclear if dead. She revives him. Talks to him.
Doctor and alien hunt Leela. She hides with Supervisor. Alien enters the room, Supervisor shoots, misses. Leela stabs him in the back, gets him. Supervisor gets whammied by dying alien. Leela runs off. Doctor holds gun on Leela, credits roll.
Doctor goes in to trance to reject the organism. Supervisor tricks them into letting him “help” them. They take TARDIS for help. Apparently Leela can fly it?
First apperance of K9!
Doctor wakes up, is diagnosed, given clue. Meets K9.
Supervisor grabs another doctor. Supervisor and doctor grab two more doctors.
Fight for control of the Doctor’s body. Doctor has station doctor make a quickie clone of he and Leela, will live about 10 minutes.
Clones are shrunk and sent into Doctor Zero to get antidote. Credits roll.
Professor and assistants give up The Doctor to the aliens to give Clone Doctor time. Aliens come while K9 and Leela-prime slow them down.
Trip through Doctor’s brain.
K9 is taken over by the aliens, somehow. Sent to kill Leela-prime. Does so.
Professor taken by alien. Tells alien what is going on. They send in men to stop the microDoctor. Leela senses them. Doctor finds nucleus thing, talks to it. Leela goes to stop the attacker.
Doctor and nexus argue philosophy.
Leela kills attacker-clone. Uses gun to kill nucleus thing. Flee through tear ducts. Expire before getting out. Nucleus thing flees, is expanded to macro-size. Credits roll!
Doctor’s case of alien invasion fades as nucleus is removed.
Nucleus plans to be big, and breed on Titan full-sized. Doctor will feed the swarm, mwa ha ha.
Leela and K9 have a disguise so she can look infected, and then kill the nucleus. The nucleus escapes to Titan to breed.
Doctor borrows K9. Professor makes resistant strain of virus. They go to Titan to distribute it. Luckily, the TARDIS is a time machine and seems to be working today.
K9 runs out of power. Leela stops her guard, and Doctor catches her. Sends her and K9 back to TARDIS. Plans on using O2 to blow station. Works.
They return K9 to professor. K9 goes with the crew. TARDIS leaves.