In May 1915, at the height of the First World War, the huge ocean liner, the Lusitania, sets sail from New York to Liverpool. It is a civilian ship, but rumor had it that there were spies on board. These rumors are true. On the crew is thirteen-year-old Finbar Kennedy, who follows his sea-captain father onto the Lusitania. Finbar is working as a deck-hand and running messages gives him a lot of information. He begins to understand what is happening, but there is nothing he or any of the crew can do. Within sight of the coast of Ireland, a German submarine launches a torpedo that changes everything.