While shopping at an outdoor market, young reporter Tintin, accompanied by his faithful dog, Snowy, buys a model of an old ship called the Unicorn. A shady character named Sakharine with his daughter Jessica and later an American named Barnaby try to buy the model from him, but Tintin refuses. The lad discovers that the ship contains a clue about a hidden treasure, but before he can locate it, Tintin is kidnapped and given over to the custody of drunken Capt. Haddock.