Tintin and Captain Haddock are walking through the countryside of the fictional Marlinshire when they come across a Romani community camped in a garbage dump, and reunite a lost little girl named Miarka with her family there. The Romani explain that they are not allowed to camp anywhere else so Haddock invites them to the grounds of his estate, Marlinspike Hall.[1]
Haddock has been trying to get the local stonemason to fix a broken step at Marlinspike, but he is never available. Milanese opera diva Bianca Castafiore invites herself to Marlinspike Hall. Haddock, who dislikes her company, tries to leave before she arrives but trips on the broken step and sprains his ankle. The doctor puts his foot in a cast and imposes bed rest. Castafiore then arrives with her maid, Irma, and pianist, Igor Wagner. Castafiore presents Haddock with a pet parrot and fusses over him, to his great discomfort.[2]
The magazine Paris Flash claim that Haddock and Castafiore are engaged, on the basis of a misinterpreted interview with Professor Calculus. This results in an avalanche of congratulations from Haddock's friends. A television crew come to Marlinspike Hall to interview Castafiore and a mysterious photographer, Gino, appears with the crew. Suddenly, Irma informs Castafiore that her jewels have been stolen, and Tintin suspects Gino who runs away during a temporary power cut. Castafiore, however, finds the jewel-case she herself had misplaced. The next day, Castafiore shows Tintin and Haddock a copy of the magazine Tempo di Roma with a picture of Castafiore taken at Marlinspike Hall without her permission, proving that Gino was only a magazine reporter.[3]
A few days later, Castafiore's most valuable jewel, an emerald given to her by the fictional Maharajah of Gopal, goes missing. After initially questioning Irma and Nestor, the detectives Thomson and Thompson suspect the Romani. Their suspicions are heightened when they find that a pair of golden scissors belonging to Irma in Miarka's possession, though she claims to have found them. After the Romani depart, the police start looking for them. Tintin also investigates Igor Wagner, whose behaviour Tintin finds suspicious, but finds out that the musician is simply sneaking out to indulge a horse-gambling habit.[4]
Castafiore leaves for Milan to perform in the opera La gazza ladra (Italian: The Thieving Magpie). Tintin realises that the true culprit responsible for the theft of the emerald and the scissors is a magpie. He explains to Haddock that the scissors must have fallen out of the nest only to be found by Miarka. Tintin retrieves the emerald and hands it to Thomson and Thompson to return to Castafiore. The stonemason mends the broken step, only for Haddock to step on it again.[5]