In Peru in 1911, explorer Hiram Bingham is in search of the lost city of Macchu Picchu. When he arrives, he is surprised to find The Doctor and Heather. They are attempting to cure temporal hiccups through the use of time holes. Hiram is angry to find them there, but gets sucked through a time hole, which closes behind him. The whole world changes. Heather and the Doctor find themselves inside a city of eight foot tall lizard men. The Lizard men chase them and, while they are hiding, they encounter an old bearded man who believes the Doctor can save them from the Incasaurs.