Deciding to repair the TARDIS' chameleon circuit, the Doctor goes to Earth to find a real police box. But an old enemy is one step ahead of him.

The Doctor, aware that his time may soon be ending, travels to the Logopolis where a series of fateful events are set in motion.

With Nyssa from Traken unexpectedly rejoining the group, Adric aids the Monitor of Logopolis in trying to save the Doctor before time runs out. The Master, at liberty to prepare, is finally ready to reveal his true target, which unknowingly sets off the biggest catastrophe of all time.

With the universe collapsing, the Doctor forms an uneasy alliance with the Master to save it. In case all does not go well, the Watcher takes the Doctor's companions to a safe place, but his plans for them don't stop there. The one hope for all lies back on Earth.

Southern England, 1981. The universe has been saved, but at the cost of the fourth Doctor's life. The newly-regenerated fifth Doctor must rely on his friends to survive as the regeneration threatens to fail…

The TARDIS is plunging toward destruction. But even if the Doctor can escape, is yet another trap waiting?

The Doctor has arrived in the supposed safety of Castrovalva. But something is odd about the seemingly tranquil city…

The TARDIS crew are caught in a space-time trap. Escaping will mean a final confrontation with the Master.

Trying to rescue the Doctor from the Tractator's trap, Tegan lands them both in even more trouble. Turlough goes a bit mad, and reckons he knows the evil of the Tractators from old.