In a close-knit community on Ireland's west coast, a baby is found abandoned on the beach. Named Brendan by Ambrose Bonnar, the fisherman who adopts him, the baby captivates the town and the boy he grows to be will captivate them still - no one can quite fathom Brendan Bonnar. For Christine, Ambrose's wife, Brendan brings both love and worry. For their existing son, his new brother's arrival is the start of a life-long rivalry. And though Ambrose brings Brendan into his home out of love, it is a decision that will fracture his family and force this man - more comfortable at sea than on land - to try to understand himself and those he cares for.