So, the Doctor thinks a vaccine that causes cells to instantly evolve to live in any environment is a bad idea, but circumstances has him working on it anyway. What’s a Time Lord to do?
See, the Doctor has his reasons. Humanity already ruins ecosystems and the planet is already headed towards overcrowding. Making nearly immortal humans capable of living anywhere will greatly decrease the quality of life for, oh, everybody, but even he will admit that Dr. Kurdi comes across as rather brilliant. She’s also unethical since the one man who died, the one the Doctor did an autopsy on, had only come to her clinic with a case of food poisoning when she tested the stuff on him without his knowledge. Still, with Jo’s life on the line, the Doctor will do what he can to complete the process.
That he got done in a half hour. He spent a couple more hours engineering a cure for the vaccine. He plans to give Jo the vaccine, and then he’ll follow up with the antidote. Kurdi doesn’t get it. The Monk doesn’t care. He’s in it for the money anyway.
Oh, but then Patient Zero Harriet manages to break loose and starts giving the treatment to, oh, everybody in the clinic, and that somehow forms some kind of hive mind. Now, all they want to do is make everybody like that, and Jo is in on the scheme. Kurdi joins them, but Jo alone knows the Doctor and the Monk are both aliens, and as such, immune. They’ll just have to die.
Why do hive minds always make people evil?
Regardless, there is one person who can help. His name is Charlie, and he’s a quadriplegic who appears to be a vegetable. A petty crook before his accident, he gained great mental powers, enough to give Jo the cure and act as invisible back-up to the Doctor to get to the Monk’s TARDIS to use the lab there to make enough of the antidote to cure everyone. That includes the squad of UNIT soldiers tricked into coming over. Granted, the Monk doesn’t have a lab in his TARDIS because he believes more in entertaining himself than science. Can the Doctor…wait, of course he can. Jo and Charlie bond a bit, especially as Charlie learns to talk over the Monk’s TARDIS speakers, and in the end, Charlie does sacrifice his life by stopping a hail of bullets sent the heroes’ way, an act that exhausts both his mind and body. As the Doctor later says, it isn’t how someone lives in the end. It could very well be how that person died. Charlie died a hero.
And that does mean the cure is dispensed. Harriet, as an innocent victim who does admit to missing that feeling of power, is let go. Dr. Kurdi and her staff are arrested for tampering in God’s domain or some such. And the Monk? He decided to make a run for it as soon as he could.
Too bad the Doctor sabotaged his TARDIS.
See, this is why it’s good to know more about science if you’re a Time Lord. But somehow, I suspect the Meddling Monk will be back.