After the events of ''[[Recap/TintinTheSevenCrystalBalls The Seven Crystal Balls]]'', Tintin and Captain Haddock arrive in Peru and report Professor Calculus' kidnapping to the authorities. Unfortunately, they are unwilling to board the ''Pachacamac'', the ship where Calculus is held since it's currently quarantined due to two cases of yellow fever. Tintin suspects this to be a lie and he and Haddock board the ship themselves. They an unable to find Calculus but confront Chiquito, who informs them that Calculus has committed "sacrilege" by wearing Rascar Capac's bracelet and will be put to death. Tintin and Haddock follow the kidnappers' trail, having to deal with assassination attempts and uncooperative authorities who seem to be afraid of something.
After saving a young native boy named Zorrino from a couple of white bullies, Tintin is approached by one of Indians involved in the assassination attempts who urges him to give up for his own safety. Tintin refuses and the Indian gives him a medallion that will "protect him from danger". Tintin and Haddock are then contacted by Zorrino, who offers to guide them to the place where Calculus is being held: the Temple of the Sun, where the last remnants of Incan civilization reside. After arriving they are captured and all three are sentenced to death by the Prince of the Sun. Tintin gives the medallion to Zorrino who shows it to the Prince of the Sun, which prompts the Indian who gave it to Tintin (Huascar, the Prince's right hand man) to explain how he got it. The Prince is impressed by Tintin's sacrifice and lets Zorrino go but Tintin, Haddock and Calculus are still sentenced to death. However, the Prince allows them to choose the day and time of their execution.
The situation looks grim until Tintin reads an old newspaper article they were carrying which prompts him to hatch a plan. He chooses the day of the execution to [[ConvenientEclipse coincide with a solar eclipse]]. During said execution, he pretends to be able to command the Sun which prompts the Inca to release them all. Tintin also convinces the Prince to release the curse on the Rascar Capac expedition. The curse is lifted and the explorers awaken.
Zorrino [[IChooseToStay decides to stay]] with the Inca while Tintin, Haddock and Calculus return to Europe safe and sound.
* AndYouThoughtItWasAGame: Calculus spends the ordeal believing this is part of some sort of movie shoot.
* BearsAreBadNews: Captain Haddock finds a nice cave to sleep in up in the Andes, only to find that it's the home of a vicious-looking bear. His expression upon being tapped on the shoulder by the bear is priceless.
* CaveBehindTheFalls: The entrance to the Temple is inside one.
* EverythingsBetterWithLlamas: A RunningGag concerns Haddock's poor affinity with llamas.
* [[spoiler:HiddenElfVillage: The Incas live at the Temple of the Sun, hidden deep in the Andes Mountains of Peru. They do interact covertly with the non-Incan Peruvians, but are otherwise intent upon keeping their continued existence a secret to the world.]]
* ModernMayincatecEmpire: [[spoiler:The Incas are an unusual variant in that they don't directly rule Peru, but the non-Incan Peruvians are scared enough of them that the Peruvians will do whatever they say.]]
* TheSavageIndian: Subverted to hell and back in ''The Seven Crystal Balls'' and this volume. The Incans are arguably the cleverest and most determined antagonists in the entire series, infiltrating Belgian society and outmaneuvering the police to strike at their victims before escaping. Tintin and Captain Haddock only manage to track them down by pure luck, and when they follow the Incas to Peru, they're very nearly killed by the Incas on several occasions. [[spoiler:Ultimately, it turns out that they targeted the Belgian archaeologists because they thought that the archaeologists had violated the Incan tombs in search of treasure. When Tintin explains that the archaeologists were only seeking knowledge, the Incas immediately lift the curse.]]
* SolarPoweredMagnifyingGlass: [[spoiler:This is how the Incas plan to light the fire that will burn the protagonists at the stake. It's definitely a case of ArtisticLicenseHistory, since real pre-Columbian cultures would have been very unlikely to resort to such a contrived method of starting a fire.]]
* WhatYouAreInTheDark: When the disguised Incan prince sees Tintin defend an Incan boy from some white bullies, he is impressed enough to help him.