Tá Tintin agus a ghadhar dílis, Báinín, sa tóir ar bhuíon idirnáisiúnta brionnóirí airgid. Ina measc tá an Dr Müller, a bheidh ina dheargnamhaid ag an iriseoir óg. Tagann Tintin slán ó iarracht ar é a dhúnmharú ach tá a thuilleadh dainséar roimhe nuair a thugann leideanna chomh fada le Poll Dubh in Albain é. Is ann a chloiseann sé faoin mBrúid a chónaíonn i gCaisleán na Binne Móire ar an Oileán Dubh. Tugtar rabhadh dó gan dul in aice an oileáin ach níor theip ar fhear – ná ar ghadhar – an mhisnigh riamh!

Tintin and his faithful dog, Báinín, are on a quest to track down a bunch of international money forgers. Amongst them is Dr Müller, soon to be one of Tintin’s most ruthless enemies. Escaping with his life after being shot, Tintin faces further close calls as he unearths clues which lead him to the furthermost isles of Scotland. This is where he discovers the dark legend of An Bhrúid, a monster incarcerated within the ruins Caisleán na Binne Móire on An tOileán Dubh. Ignoring any monstrous tales, Tintin and Báinín take a boat to the island to challenge the legend that lies ahead.