In the bustling European city of Brussels, young and curious reporter Tintin, accompanied by his loyal dog Snowy, purchases a model ship named the Unicorn at a market. Soon after acquiring the ship, he is approached by two individuals, the sinister Sakharine and the mysterious Barnaby, who both express a strong interest in buying the ship from him. Tintin refuses their offers, intrigued by the ship's importance. His curiosity piqued, Tintin discovers that the model contains a secret clue to the location of a hidden treasure related to the legendary sunken ship commanded by Sir Francis Haddock. However, before he can delve further into the mystery, he finds himself entangled in a dangerous adventure when Sakharine's men kidnap him and bring him aboard the SS Karaboudjan.

Aboard the ship, Tintin befriends the perpetually inebriated Captain Haddock, the last living descendant of Sir Francis Haddock. Tintin and Haddock escape their captors, but not without facing a series of perilous situations. With the determined Sakharine on their tail, they embark on a globe-trotting journey that requires them to solve riddles, brave the deserts, and navigate the high seas. Their quest brings them closer to discovering the true story behind the Unicorn shipwreck and the ancient conflict that casts a shadow over the coveted treasure. As alliances are forged and enemies close in, Tintin's quick wit and bravery are put to the test in the race to unravel the centuries-old mystery.