It's 1740 . . . The Firefly is taken in the night by pirates who sail the Caribbean. The ship's boy and a handful of men are set adrift in a jolly-boat. Without food or water the half-starved men eye up the young boy. Astonishingly, a mysterious Mr Wicker saves the boy by turning him into an unearthly creature—an invisible flying boy with beautiful emerald-green wings. When the boy is drawn to a ghost ship sailed by Captain Bass, he learns of the dangerous power of a magical astrolabe which Mr Wicker desperately seeks—and why Wicker must never find it. The boy cannot trust Wicker . . . but is there anyone he can trust? Captain Bass? Sophie Blade, the pirate's daughter? And who can return him to himself?