The Doctor (Baker) and Leela (Louise Jameson) indulge in their own Fantastic Voyage this week. This four-part story, written by Bob Baker and Dave Martin originally aired from 1 October to 22 October, 1977.
A three-man rocket is returning to Titan Base when they pass through a strange cloud like substance in space. It actually proves to be The Swarm, a sentient virus, that infects the crew and upon their arrival, begin to take over the base as well, with the unnerving phrase, “Contact has been made,” every time they take over a new body.
The Doctor, aboard the TARDIS, and back in the old control room receives the emergency call from the rocket, and he and Leela arrive on Titan Base to help. But it may already be too late, as the possessed crew are preparing the base for the Swarm’s needs, and it seems the Doctor has already become infected! Leela is left untouched, as it seems she operates more on instinct than intelligence (ouch!).
While the Doctor tries to fight the infection, he realizes he may need help, and he and Leela make for a nearby medical station located in an asteroid belt. It is here, that while the Doctor sinks himself into a about of self-induced coma, that we are introduced to Professor Maruis (Frederick Jaeger) an expert on alien diseases, who has a mechanical sidekick of his own creation, one that takes a bit of a liking right off the bat to Leela, the robotic dog, K9 (Star Wars had just come out after all).
Now unless you know all manner of Doctor Who details… you’re asking yourself how did Sarah-Jane (Elisabeth Sladen) show up in School Reunion, a few regenerations down the line, with K9, if she’d already left the TARDIS? Well, before her own show, The Sarah-Jane Adventures, she discovers a crate in her Aunt’s attic in Croydon, inside is K9 Mark III. This was the one and only episode of K9 and Company, entitled “A Girl’s Best Friend.”
When the Doctor rouses himself from his coma, he converses with Marius about cloning, and has two made, one of himself and one of Leela, while the med center is slowly overrun by infected personnel. The clones are miniaturized, and injected into the Time Lord, so that they can seek out the virus seed, the Nucleus, within him. He and Leela travel trough his brain, eventually confronting the Nucleus, and tricking it out of the Doctor’s body…
It’s strange that we learn that the clones only have a life span of about 11 minutes, but seem to live a little longer than that, an episode and a half a least… but perhaps it has something to do with a reduction in size…
Once the Nucleus has left the Doctor, its human servants try to get it somewhere safe, for its spawning, but the Doctor and Leela find a way to destroy it!
As the story winds up, Marius reveals he is returning to Earth, and would like K9 to travel with Leela and the Doctor, before the Doctor can protest K9 is aboard, and they are on their way to confront The Image of the Fendahl!