Doctor Who and the Keys of Marinus

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!