Parts: 7
Writer: John Lucarotti
Airdates: 22 February 1964 - 4 April 1964
Production Code: D

Episode Titles: The Roof of the World; The Singing Sands; Five Hundred Eyes; The Wall of Lies; Rider from Shang-Tu; Mighty Kublai Khan; Assassin at Peking

Doctor: first
Companions: Susan, Ian, Barbara

Story: While repairs are being made to the damaged TARDIS, Ian and Barbara brave the snowy landscape outside to collect wood. They learn that they are in Asia when confronted by Mongols who want to execute them for being evil spirits. They are saved by a man who Barbara suspects is Marco Polo, indicating the time to be around 1289, and they then join his group of travellers heading to the court of Kublai Khan.

But the long journey is not to be a rest period for the TARDIS crew. Polo refuses to let the Doctor into his "flying machine" because he is planning to use it to buy his freedom from the Khan. One of the Mongols, Tegana, also seeks possession of the TARDIS, but he hopes to get it by poisoning the others.

Tegana's greed causes him to become a more and more dangerous threat to the TARDIS crew, and as the peril to their lives grows ever greater, the four time travellers must use their wits to try to escape while keeping themselves alive.