What was the name of the Fourth Doctor's last storyline?

Answer 1

The fourth Doctor (Tom Baker) finished his time in the show with a story called Logopolis by Christopher H Bidmead. A four parter, it tells the story of how the Master tries to take control of the Universe (no suprises there!) using the technology of the Logopolitans which is called Block Transfer Computation. He makes a mess of things by not really understanding what he's doing and kills off Logopolis. This is unfortunate as it turns out Logopolis is holding the Universe back from the brink of collapse and the Master's meddling makes the Causal Nexus to start unravelling. Or whatever. Using some techno-babble, the Doctor and the Master knock up a device to keep things running, but not before Nyssa's home planet is destroyed. In the end, the Doctor falls off a giant radio telescope and dies, regenerating into Peter Davison. It's a good story, with some weird stuff going on with the Watcher and some very peculiar happenings inside the TARDIS. Things to try and avoid watching too closely include Adric and his moody acting, and Tegan, especially when she exclaims "Earth!". Tom Baker's performance is strangely joyless and intense, perhaps because it's his last one, but he still gets some dark humour in there, like when he tries (badly) to comfort Tegan ("There, there"). Recommended, as it's enjoyable and marks the end of an era for the programme.