Castrovalva: Part 3—Season 19

Something is wrong with Castrovalva, but the Portreeve cannot help identify the problem.

Castrovalva: Part 2—Season 19

The Zero Room is gone and the Doctor's regeneration is unstable.

The Doctor tries to recuperate within the Zero Room.

With the fate of the universe at stake, the Doctor and the Master must collaborate.

The Master is loose on Logopolis and is determined to learn the planet's secret.

The Doctor travels to Logopolis where a series of fateful events are set in motion.

To repair the TARDIS' chameleon circuit, the Doctor goes to Earth for a real police box.

Melkur is the new Keeper of Traken and the Doctor discovers the truth about his enemy.

Melkur is poised to take control of the all-powerful source manipulator.

As Melkur begins to return to life, he manipulates Kassia into doing its bidding.