O chionn fhada, ann an uisgeachan a’ Charibbean, far an robh spùinneadh cumanta, bha fear de shinnsirean a’ Chaiptein Habairadag an sàs ann an strì an aghaidh an spuinneadair ainmeil, Ragam Ruadh. Chaidh an long aige, an t-Aon-Adharcach – agus an ulaidh na broinn – a chur gu aigeann na mara. Ach, nuair a lorgas Tintin modail dhen t-soitheach, tha e a’ faighinn fiosrachadh neo-choileanta a dh’fhaodadh a chur gu làrach dhìomhair na luinge. An tèid aige air na criomagan fiosrachaidh a chur ri chèile?

Long ago, in the pirate-infested waters of the Caribbean, one of Caiptein Habairadag’s ancestors was embroiled in a battle against the infamous privateer Ragam Ruadh. His ship, the Aon-Adharcaich, was lost to the deep along with the pirate’s booty, but when Tintin finds a model of the warship, a clue appears which could lead to the treasure’s location… will Tintin be able to decipher the mystery?