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!