Owen Kerrigan, the cantankerous lighthouse keeper of a remote Irish island, has been estranged from his only brother Patrick for most of his adult life. His only solace has come from immersing himself in the legend of a long lost treasure belonging to the wreck of a Spanish Armada galleon that is rumoured to be hidden beneath his light. But after tunnelling in vain for years, Owen is issued with a sudden eviction notice. In desperation, with only days left to find the gold, Owen begrudgingly asks his brother for help. Hoping it may help to rebuild their relationship after more than thirty years of silence, Patrick reluctantly agrees. As they attempt to unearth the fortune, Owen becomes increasingly drawn to Ellen, an enchanting descendant of the Pirate Queen, Grace O'Malley, who ruled the island at the time of the Armada. As Owen's imminent eviction looms, they race to solve the riddles ingrained in the ancient folklore of the island and realise that Ellen may unwittingly hold a vital clue to finding the treasure. But the rift which kept the brothers apart for so long threatens to thwart both Patrick's hopes of reconciliation and Owen's dream of finding the fabled hoard.