Maire O’Donnell is a loving woman as rare as a double rainbow. Joyful, warm and caring, she adopts a young orphan named Tomas and whisks him off to a new home on remote Corrie Island, off the coast of Ireland. Maire shares with Tomas the joys of her island home and introduces him to the whimsical local folklore, including the secret of the seals, and teaches him that everything you need is inside of you- if you really look. But Maire's stern husband Alec silently disapproves of Tomas' timidity and halting speech. He can't hide his disappointment that Tomas isn't the kind of child he was hoping for and his reluctance to get to know the boy makes Tomas unsure of whether he really belongs. Soon though, Tomas too falls in love with his home, befriending local children, descending into a secret bat-filled cave, and saving a stranded baby seal. When tragedy strikes however, Tomas is faced with his greatest challenge yet...