This book tells about the survival of Francisco De Cuellar's, captain of the San Pedro, after the shipwreck off the Sligo coast. He was washed up on Streedagh, injured, and naked. Then he realized he was in danger: twelve of his compatriots were hung in a ruined monastery. He had to hide from troops and some locals until he eventually found refuge with chieftains of the clans O'Rourke and McClancy, before making his way northward to and escaping to Scotland.