Someone on the island is breaking into houses, killing pets, and hurting innocent people. The authorities are on the case, but sixteen-year-old Aggie Callaway and her best friend, Babs Butler, aren't convinced they are giving it their all. Determined to find out who is behind the nightmarish events, the girls do a little sleuthing on their own--never dreaming that the very individual they are seeking is watching their every move.