The Keys of Marinus is a serial in the British science fiction television series Doctor Who, which was first broadcast in 6 weekly parts from April 11 to May 16, 1964.
The planet Marinus is under threat from the Voord. The only hope of stopping them is to recover the keys to a machine known as the Conscience of Marinus, which have been hidden around the planet. The First Doctor, Susan, Ian and Barbara are forced to search for the keys in a variety of dangerous locations in order to restore order to Marinus.