Recap / Doctor Who S3 E10 "The War Machines"
"Doctor Who is required- What? His name isn't 'Doctor Who'? Well, it's too late to remind me- we already used up all the retakes the studio is allowing!" note 

"I dig your fab gear!"
— A nightclub owner likes the Doctor's clothes.

The TARDIS arrives in contemporary London, and the Doctor and Dodo visit the Post Office Tower, where they meet Professor Brett and his new super-computer WOTAN, which can think for itself and is about to be plugged into a worldwide computer network.

I think we can all see what's about to happen here, can't we?

WOTAN decides that machines are superior and should rule the world, and hypnotises humans into building the titular War Machines, which turn out to be more than a match for the army. The Doctor uses a magnetic field to capture one, which he then reprograms to destroy WOTAN.

Dodo, having been hypnotized by WOTAN, decides she's had enough adventure. Since she's back in her own time, she decides to stay there. In one of the lamest departure sequences for any companion, she isn't seen after episode two and says goodbye to the Doctor in episode four via a note, delivered by Polly. The Doctor leaves, but not before Professor Brett's secretary Polly and able seaman Ben Jackson enter the TARDIS while trying to return a missing TARDIS key to the Doctor.

Watch it here.