In black-and-white broadcasts, Professeur Calculus shares a heartfelt plea to help end world hunger, a broadcast that fills his mailbox with letters and parcels from around the world. Among the gifts is a remarkable blue orange, capable of thriving in desert conditions and even glowing in the dark. It arrives from Professeur Zalamea but arrives without any explanation or note.
That very night, two thieves break into Marlinspike Hall and steal the mysterious blue orange, leaving Calculus and his companions with a pressing mystery and a dangerous mission. With no other option, Tintin, Capitaine Haddock, and Snowy decide to follow the trail to Valencia, where the fruit’s alleged inventor, Zalamea, is said to reside. The journey takes them into a landscape that will be filmed across Burjassot, Simat de la Valldigna at the Monastery of Santa María de la Valldigna, Gandia, and Xàtiva, painting a vivid backdrop for the unfolding adventure.
Upon arrival, they discover that Zalamea is absent from his hacienda, and instead they meet his wary cousin. Calculus is kidnapped, forced to assist Zalamea in perfecting the blue oranges. The plan is to use neutron bombardment to mature the fruit in five days, but the result is unsettling: the oranges mature yet taste bitter and salty, rendering them inedible.
Tintin befriends a local boy, [Pablito](/actor/pedro-mari-sn Sanchez), who leads him to a gang hideout and exposes a troubling clue: a man with a blue dragon tattoo on his hand was seen attacking a boy who was to deliver the parcel to Zalamea. Interpol detectives Thomson and Thompson arrive on the scene, add a splash of comic tension with a bull, and begin investigating Zalamea’s disappearance.
The locals guide Tintin and Capitaine Haddock to the hotel of a man named Fernando, whose radio signals connect to a larger network. Tintin picks the lock, overhears Fernando speaking to his chief about a rendezvous, and the duo tails him—only to be knocked unconscious and taken away themselves. Meanwhile, Thomson and Thompson check into a hotel only to be outwitted by the villains, who use doubles to bluff their way out of danger. Tintin and Haddock awaken in a grain silo and are rescued when Snowy lets down a rope to bring them to safety.
Back in town, the pair are chased by the authorities through a bustling market, but a timely intervention from Bianca Castafiore helps them slip away. A delegation from the visiting Emir of Sakali arrives, and Tintin and Haddock reconnect with their young allies. They hatch a plan to return to Zalamea’s hacienda to uncover Estensoro, Zalamea’s loyal servant, and confirm the deeper role he plays in the kidnapping. Using animals tethered with pans as a distraction, they infiltrate Estensoro’s room and locate a radio identical to Fernando’s, proving Estensoro’s involvement. Haddock’s accidental swig of Estensoro’s whisky triggers a series of discoveries, revealing Zalamea’s secret documents and hinting at the true identities behind the conspiracy.
Back at the villains’ hideout, the professors manage to broadcast their whereabouts, spurring Estensoro to hurry to his boss with the news. Tintin and Haddock chase the trail, and after a brief struggle, Estensoro is subdued—but the professors remain missing. The villains, uninterested in the Thom(p)son twins, leave them tied up as Snowy uncovers an agal belonging to one of the Arab kidnappers. Tintin pieces together that the Emir of Sakali is connected to the Arab foe described by Zalamea.
The Emir’s luxury yacht sits at the docks, and Tintin and Haddock mount a daring rescue attempt. The professors are drugged and their loud voices alert the guards, capturing both Tintin and Haddock in turn. A chaotic confrontation erupts, and a swarm of cheering children—warned by Snowy—arrives to turn the tide. The villains are cast into the sea, the Emir is subdued, and the police arrive to restore order.
Returning to Marlinspike Hall for a celebratory tableau, everyone reflects on what lies ahead: they hope to perfect the orange’s cultivation within ten years and to begin growing other crops, like wheat, potatoes, and eggplants, in the desert. Just then, Thomson and Thompson crash into a fountain in a slapstick finale, and a line of greedy dogs devours the “THE END” sign, leaving the moment both chaotic and charming.
