Seventeen-year-old Sebastien de L'Esperance and his friend Guillaume have fought to keep the British from getting a foothold in Ile Royale (now Cape Breton Island) ever since the young men came from France two years ago. Britain has blockaded Louisbourg, and supplies for the 4000 inhabitants are running short. Despite Louisbourg's massive defences, if cut off from supplies provided by France, it cannot survive. Both young men are members of the Compagnies Franches de la Marine. They are sent out on scouting missions that provide valuable information about the British troops - troops which outnumber the French three to one. When British warships arrive in force, Sebastien vows to defend the town, his friend Guillaume, and the woman he loves.