Tintin and Captain Haddie find a model of a 17th century warship, the Unicorn — a vessel once captained by one of the Captain’s maritime ancestors, Sir Graeme Haddie, who, under onslaught, lost the ship to the infamous pirate Rachlan the Reid. The pirate proceeded to load the Unicorn with all his captured booty, before the ship was holed and the treasure succumbing to the deep. But a clue to the treasure’s location lies within the model of the Unicorn… will Tintin be able to decipher the mystery, and find Rachlan the Reid’s lost treasure?