Back in the chamber. DOCTOR 2: That's very clever. He moves through some of the same areas passed earlier by Leela and the Doctor. MARIUS: Micro-cloned copies have been injected into his brain and are even now trying to hunt down and destroy the Nucleus. They can attack us from behind. They take cover.
Plan: A: a defense; Q: What does the medical center mount against alien forces trying to take the comatose Doctor? A: clones; Q: What is Leela and the Doctor made of? A: Leela; Q: What character is cloned to hunt down the infection in the Doctor's head? A: the intelligent infection; Q: What is in the Doctor's head? Summary: The medical center mounts a defense against alien forces trying to take the comatose Doctor while clones of Leela and the Doctor go microscopic so they can hunt down the intelligent infection that's in his head.