Cathy, Nancy, and Mildred are on their way to Long Island to plan a triple wedding. When they try to meet with Georgia Hampton, a wedding planner who leads whale-watching tours, they discover her body upon her boat.

Teaming up again, the trio investigate the crime. Suspects include Georgia's sister who is a partner in their wedding planning business, an artist who is a naturalist and conducts whale-watching tours, several couples whose relationships ended after consulting with Georgia, and employees of the tour company.

Reuniting with her great aunt after many years, Cathy learns that another suspicious death has occurred at Captain Sharp's Whale Watching Tours. Can they solve the mystery, or will their efforts sail out to sea?