Marco Polo, the forth story of Doctor Who's first season, was first broadcast in March-April 1964, starring William Hartnell as the Doctor. All seven episodes are missing from the BBC archives, and they remain only as a handful of telesnaps and rehearsal shots, together with poor quality audios of the episodes.

The story begins as the travellers arrive in the Himalayan Mountains in the late 13th Century. They are rescued by the Venetian Marco Polo, and due to a misunderstanding about the nature of the TARDIS, are forced to travel with him to Kublai Khan's palace at Peking and try to prevent the time craft being given to the Emperor as a gift. Meanwhile, one of Polo's party has his own treachery planned...