This is the first Doctor Who story set in an historical period and context, avoiding science fiction elements beyond establishing the plot where the Doctor and his companions have travelled to the past. None of this episode's footage has survived.


The TARDIS crew lands in the Himalayas of Cathay in 1289, their ship badly damaged, and are picked up by Marco Polo's caravan on its way along the fabled Silk Road to see the Emperor Kublai Khan. The story concerns the Doctor and his companions' attempts to thwart the machinations of Tegana, who attempts to sabotage the caravan along its travels through the Pamir Plateau and across the treacherous Gobi Desert, and ultimately to assassinate Kublai Khan in Peking, at the height of his imperial power. The Doctor and his companions also attempt to regain the TARDIS, which Marco Polo has taken to give to Kublai Khan in effort to regain the Emperor's good graces. They are finally able to thwart Tegana, and, in doing so, regain the Emperor's respect for Marco Polo, who allows them to depart.