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 stays with the Inca while Tintin, Haddock and Calculus return to Europe safe and sound.
Tropes
- Alternate History: The story features a secret Inca holdover whose members have great influence over the entire Peruvian population, to the point even the cops themselves are implied to serve them out of fear. This echoes the real life Neo-Inca State of Vilcabamba, an excision of the Inca Empire that continued warring against the Spaniards (and the rest of the empire, most of which had sided with Spain) for almost a century before being assimilated. It seems that in this version, either Vilcabamba was not fully assimilated or there was a separate holdover the Spaniards and their allies never had notice of.
- 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.
- Bird-Poop Gag: One of the Thom(p)sons asks what guano is and Captain Haddock is not sure how to put it, and then a bird poops on the detective's hat and Haddock says, "Guano? Well, that's a free sample!".
- Bizarre Beverage Use: In the end, Captain Haddock fills his mouth with water from a drinking fountain and spits it out on a llama's face, as revenge for all the llamas who spat on him earlier in the story.
- Cactus Cushion: Captain Haddock jumps off the Runaway Train carriage and barrels out of control down the rocky slope to land in clump of prickly pear.
- Cave Behind the Falls: The entrance to the Temple is inside one.
- Character Witness: When the disguised Incan priest sees Tintin defend an Incan boy from some white bullies, he is impressed enough to help him.
- Chekhov's Gun: The crumbled newspaper clipping holds an important clue.
- Comically Missing the Point: Professor Calculus is convinced that the Incas are making a film and he and the others are appearing in it.
- 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. Hergé later discovered this oversight on his part, and declared he would have written a different ending if he had known about this.
- Cultural Posturing: All but stated with the Incas, who own a secret settlement in the mountains where they have carefully retained all of their Pre-Hispanic culture, including rituals, weapons and et caetera, but at the same time they have members infiltrated in the Peruvian society with perfect competence and are clearly aware of modern society — although there are still fields they are not familiar with, namely astronomy. This proves to be a plot point.
- Death Glare: Captain Haddock gives an angry stare to a llama. Unfortunately for him, it counters by chewing his beard off.
- Entertainingly Wrong: Finding Calculus's dowsing pendulum, Thompson and Thomson try to dowse with it in tracking him down. They get the general details right, but the precise location wrong, i.e. it takes them out of Peru and all the way to Paris, instead.
- "Eureka!" Moment: Tintin has one when he reads the article from the newspaper clipping.
- Failed a Spot Check: When Haddock finds a cave and deems it safe. Cue a Bears Are Bad News moment for him.
- Gilligan Cut: When the Incas want to force Haddock into a sacrificial robe, he responds with a Big "NEVER!". Cut to him being dressed in said robe.
- Grapes of Luxury: Downplayed. Once Tintin decides on a date for their death, he and Haddock are relocated from their prison cell to a royal apartment with a bowl with fruits (including grapes) waiting for them.
- 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.
- Historical In-Joke: Possibly accidental, but it's notable that the high priest who becomes secretly favorable to the European heroes against the more zealous emperor is named Huascar. In real life, Huascar was the name of the original Inca emperor before his brother Atahualpa overthrew him, which had the effect of pitting most of the empire against Atahualpa... and in favor of the Spaniards once they arrived.
- Idiot Ball: The Incas had full knowledge of what eclipses were and how to predict them, and thus wouldn't freak out at Tintin's stunt. Hergé admitted that this was "a huge blunder" on his part.
- It May Help You on Your Quest: The medal Tintin receives from a stranger.
- Kidnapping Bird of Prey: Snowy is captured and taken away by a condor, so Tintin goes off to rescue him.
- Make It Look Like an Accident: A variation. The Peruvian stationmaster refers to the incident with the decoupled train car as an accident, and fails to believe Tintin when the latter refers to the incident as 'attempted murder' (possibly due to fear of retribution from the Incas if he did believe Tintin).
- Mayincatec:
- Some pieces of artwork used here and there are either pre-Inca or not Inca at all, like Staff God of the Tihuanaco Empire, and there is mention of an Inca writing system, which didn't exist in real life. Those Incas seem also a bit more sacrifice-happy than real deal were, but this can be explained because their interactions with outsiders have rarely been positive.
- Hergé, who got a lot of his information from National Geographic, mixes up the Inca with the Maya with the 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 (could be an in-universe misidentification, however). 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 rest of the Peruvians are scared enough of them that they will do whatever they say.
- Never Smile at a Crocodile: Tintin has to kill attacking crocodiles.
- Rail-Car Separation: Tintin and Captain Haddock find themselves on a runaway coach while travelling by train on the way to find Calculus. The stationmaster at the next station then mentions it was the first accident on the line, but by that point Tintin is already convinced it wasn't an accident at all.
- Runaway Train: Tintin is set up to be killed when the Incas decouple his train car. He can escape in the last moment.
- 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.
- Shown Their Work: Thanks to a National Geographic magazine, Hergé was able to get many details correct, such as Inca dress and architecture. However, he only uses these touches where it fits the story, so there are no "tourist moments" in the story showing off the temple, for instance. Of course, his limited sources meant he still made some mistakes (like assuming the Inca had a writing system and did not know about eclipses), but he corrected the former mistake partly in a later edition, and stated that he would have changed the eclipse ending if he had the chance.
- Skewed Priorities: On the rope, Haddock holds on to his hat no matter what.
- Soft Water: Tintin manages to escape a train launched at full speed by jumping as it goes over a bridge that seems to be dozens of metres (a hundred feet) high. It works perfectly, even though he commented earlier that he could not jump to the ground, as the speed would kill him.
- 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.
- Unspoken Plan Guarantee: Tintin keeps his plan regarding the Convenient Eclipse to himself, fearing that he would otherwise raise false hope in Haddock. Naturally, the ploy goes as planned.
- Voodoo Doll: Apparently, the high priest used this kind of witchcraft to invoke the illness in the explorers.
- You Don't Want to Catch This: A rare villain example occurs when the crew of the ship where Calculus is being held put up a quarantine flag and have a crooked doctor declare the ship out of bounds. However, Tintin isn't fooled.
- You No Take Candle: Zorrino speaks this way.
