In Kilmor Bay, the longest day begins. While the rain turns everything around into a thick gray veil, calm in the harbor is broken by thunder and sudden fiery flashes. But this isn’t a storm and not lightning—this is continuous volleys from the eight cannons of the “Mary Grey,” the legendary ship of Captain Spencer.
A pirate is settling scores with the twins, Jason and Julia Cavenant. The boys had to fight the most terrible enemy without the help of Ulysses Moore, who still hasn’t managed to defeat him.