After the events of 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 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 decides to stay with the Inca while Tintin, Haddock and Calculus return to Europe safe and sound.
- And You Thought It Was a Game: Calculus spends the ordeal believing this is part of some sort of movie shoot.
- Bears Are Bad News: 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.
- Cave Behind the Falls: The entrance to the Temple is inside one.
- Convenient Eclipse: Oddly enough, the Incas do not know about the impending eclipse, despite worshipping the sun and having covert contact with the modern world.
- Everything's Better with Llamas: A Running Gag concerns Haddock's poor affinity with llamas.
- Hidden Elf Village: 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.
- Kidnapping Bird of Prey: Snowy is captured and taken away by a condor, so Tintin goes off to rescue him.
- Mayincatec: The Incas are portrayed rather sympathetically, as even though they try to sacrifice the heroes, their interactions with outsiders have rarely been positive. Oh, and they suck at astronomy, as a plot point. On the whole Hergé, who got a lot of his information from National Geographic does not mix up the Inca with the Maya except with reference to the prophetic inscription mentioning the retribution that will befall the violators of Rascar Capac's tomb, which plays a large part in The Seven Crystal Balls. The Incas, unlike the Mayas and Aztecs, had no system of writing. The original version of The Seven Crystal Balls, serialized in Le Soir, also contained a lead disc with symbols "resembling Aztec or Inca signs", but Hergé excised the panel that showed it and texts that mentioned it when the album version was produced.
- Misplaced Wildlife: Alligators appear in this album, even though crocodiles would be more accurate. The bear also does not resemble the spectacled bear (the only kind found in South America).
- Modern Mayincatec Empire: 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.
- The Savage Indian: 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. 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.
- Solar-Powered Magnifying Glass: This is how the Incas plan to light the fire that will burn the protagonists at the stake. It's definitely a case of Artistic License – History, since real pre-Columbian cultures would have been very unlikely to resort to such a contrived method of starting a fire.
- Fridge Brilliance sets in when one considers that the Incas in the story have been covertly interacting with the outside world for decades, if not centuries since the Spanish conquest. They are shown to be sophisticated enough to plan the cursing of the Rascar Capac expedition and Professor Calculus' kidnapping on another continent. Most or all of them know Spanish, since it is highly unlikely that Tintin and Haddock would know Quechua or any similar languages. Therefore it is only logical that the Incas would have adopted the use of the magnifying glass, among other technologies, in their everyday life and ceremonies. All of this of course makes it all the more inexplicable that the Incas would fall for a simple Convenient Eclipse ploy.
- What You Are in the Dark: When the disguised Incan priest sees Tintin defend an Incan boy from some white bullies, he is impressed enough to help him.