Young Kitty owns a small trading vessel called the Storm Siren that runs between Totnes and Dartmouth in Devon delivering soap from the family owned factory. Her crew consists of Florence, George, Denzel and Finley. On a trip to Dartmouth they rescue a young lad called Archer from the fast flowing river. Poor Archer had been trying to pursue a Danish ship called the Skuldelev to rescue his father who had been press ganged. With the help of their friend Amos and later the customs officer Mr. Tubman they hatch a daring plan for a rescue.