Tintin and Captain Haddock travel to Peru in search of Professor Calculus, which are on board a ship bound for that country called Pachacamac, but can not release it. After much research, they realize that Calculus would be held in Inca pyramid in the middle of the jungle, last Inca settlement, so they decide to go there.
After crossing the Andes and the jungle (in company with a local girl called Skunk and guides them), arrive at the site where is located the pyramid. They are captured and learn that Calculus was to be sacrificed along with them, for committing the sacrilege of wearing clothes of a sacred mummy.
Finally, Tintin uses a cunning (an eclipse occurred in the same place) to free them all and get back together.