Marinus - a remote force-shielded island set in a sea of acid, governed by... the Conscience - the ultimate computer which rules and balances the gentle life of Marinus, guarded by... Arbitan the Keeper - ruthless protector of a peace-loving race threatened by... Yartek - Warlord of the brutal sub-human Voords, sworn enemy of Arbitan and of Marinus, who has within his grasp... The Keys of Marinus - The Conscience's vital micro-circuits, the doors of good and evil.

Can the Doctor find the hidden circuits in time? Arbitan's command was "Find them, or DIE!"

Novelization of the Doctor Who TV series; six episode story "The Keys of Marinus" (1964), script bt Terry Nation.