Every family has its secrets.

Summer, 1966: For 13-year-old Gus LeGarde, summertime always means Loon Harbor, his grandparents' idyllic fishing resort on Great Pond. The season is a grand tradition of swimming, boating, and new adventures with his best friends, twins Siegfried and Elsbeth. But this summer, everything changes when a new lodge down the shore threatens the resort - and triggers a chain of events that will transform Gus and his friends forever.

Customers are leaving Loon Harbor in droves for The Seven Whistles, owned by the wealthy LaFontaines. The Baton Rouge family arrives with better amenities and a much larger staff - among them Wilhelmina "Willy" DuPont, a young black girl whose family works for the LaFontaines. Gus and the twins immediately bring Willy into their circle - but their friendship is soon challenged when events at The Seven Whistles take a terrifying turn.

A mysterious figure haunts the windows of women and young ladies at both camps, escalating from peeper to dangerous stalker. Then the LaFontaines' spoiled and demanding daughter goes missing - and Willy's innocent older brother is arrested.

Gus soon discovers that dark secrets lurk beneath the surface of the LaFontaine family, and the stakes are higher than ever imagined as they race to exonerate Willy's brother and find the real perpetrator - before he finds them.