Marco Polo — John Lucarotti

As the TARDIS lands on a remote mountainside, the power fails and leaves the Doctor and his companions stranded without heat or water. They are rescued by the Venetian traveller Marco Polo, who tells them it is the year 1289. They join Marco's caravan travelling to the Great Kublai Khan's palace in Peking. Accompanying Marco Polo is the Mongol warlord Tegana, an emissary from the Khan's enemy, Noghai, on his way to discuss peace terms with the Khan.

Believing the TARDIS to be a 'flying caravan', Marco takes it from the Doctor and intends to offer it as a gift to the Great Khan in the hope that he will let him return to Venice. To avoid being stranded in ancient Cathay, the Doctor must repair the ship before they reach the Khan's palace. But Tegana has his own plans for the TARDIS and if he succeeds, none of them will even reach Peking...