Season 1, Episode 4 - "The Firemaker"
14 December, 1963
Ian realises that the footprint could be just an ordinary one enlarged by the snow melting. A more serious problem soon presents itself as the Doctor reports that the TARDIS has developed a major fault: all the lights have failed, the water supply has been affected and the heating is inoperative: 'Everything's gone to pot!' As Barbara points out, they are now in danger of freezing to death.
