Ever since the death of her parents, Miranda has lived on Whym Island, taking comfort in the local folklore, which claims a mysterious sea witch controls the fate of all on the island and in its surrounding waters. But when a terrible boating accident takes the lives of several of her friends, and Miranda is rescued by a mysterious boy who haunts her dreams, she finds refuge in late-night swims---and meets Christian, a boy who seems eerily familiar, but who is full of mystery.