Doctor Who and the Keys of Marinus

In 1980, Doctor Who and the Keys of Marinus was released by Target Books.

Cover blurb
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!'