Yes ! L'Ile noire ! I really love this album. And maybe my first contact with scot culture (I was 7 yrs old when I read the story). There is a legend. The old and ruined castle in the story came from Brittany (bay of Morlay near Plouézoc'h). But others say the famous castle on the island came from Le Dramont and l'île d'or (Golden Island) near Saint Raphaël in the south of France.
And if that was a real island in Scotland ?