The Voord seek to control the Conscience of Marinus, leading to direct opposition with Arbitan and indirect conflict by proxy with the TARDIS crew.

Susan recounts her harrowing encounter with a frogman in the corridor—how she was grabbed, nearly killed, and then saw the attacker fall dead with a knife in his back. The …

After the TARDIS crew reluctantly agrees to Arbitan’s blackmail—retrieving the five keys of Marinus to prevent the Voord from seizing control—Barbara impulsively activates a teleportation device, vanishing instantly. Arbitan, sensing …