A small segment of the war of 1812 provides melodramatic accents for an eventful summer around St. Michael's, Maryland, in 1813. Bob Pennington, a ship owner's son, and his friend, Jeremy, are out fishing on a day after warnings of a lurking British fleet. The boys see suspicious craft and as they go to spread further word at home, there follows the series of events leading up to the later unsuccessful attack on St. Michael's. Through Edith Lang who comes to the Pennington's as a refugee from a bay island, Bob is instrumental in catching a British spy, Gaskin. Through Gaskin's threat on her father's life, Edith is prevented from telling all she knows, but the means for Gaskin's capture come in time to keep full details of St. Michael's defenses from enemy ears. Political issues are sketched in as background, but the manner of telling lessens its importance.