While driving a motorboat around the Twin Lakes, Nancy and her friend
Helen get caught in a dangerous storm. Luckily, they are rescued by
another teenage girl in a rowboat. They soon learn that their rescuer is
Laura Pendleton, whose mother has recently having passed away. Laura has
come to meet up with her new guardians, but something isn't quite right
about them. Nancy investigates the situation, and soon she stumbles upon
a shocking surprise in the cellar of a bungalow!