When, after a four-year absence, seventeen-year-old Squid returns to her childhood home on a remote lighthouse island off British Columbia with her young daughter in tow, she and her parents try to come to terms with each other and the painful events of the past, especially the death of her older brother.

Every night Lampie, the lighthouse keeper's daughter lights the lantern which warns the ships away from the rocks, but when the light goes out one night, a ship is wrecked and Lampie is sent to the Admiral's Black House in disgrace--there she finds and befriends the Admiral's son, who was born with a tail, and together they are pulled into an adventure of mermen and pirates, and secret identities long concealed but soon to be revealed.