Deb Connolly drowns after falling overboard on an afternoon sail and her husband commits suicide two days later. Annie Beckwith is distraught over the loss of her sister and her sister's husband, and tries to get on with her life. Chief Joe Silva and the other authorities don't doubt the report of Deb's sailing partner, Cecily Harris, a woman known to be afraid of the water and unfamiliar with sailing. But a sharp eye at the marina where the sailboat has been dry-docked discovers evidence of tampering with a key piece of equipment, and the accidental death no longer seems so obvious. In the idyllic setting of Mellingham, Annie Beckwith decides to get to know her sister's neighbors better in the hope of learning something that will help her understand Deb's death. Chief Silva wants to know who tampered with the sailboat and why. Mellingham is beautiful in the summer and this year Joe's stepson, Philip, wants to learn to sail. Joe rents a small boat and teaches the boy how to sail and the rules of the water. Philip is a natural on the water, and this turns out to be a very good thing when he finds himself sailing for his life.