When Deborah Strong accepts an invitation for a reunion with high school friends who will all be turning fifty, she anticipates a lovely Fourth of July weekend in Maine. Her friend Brenda's summer house is rustic and beautiful, but from the moment Deborah arrives, something seems wrong. Old rivalries flare between Brenda and Rachel, and Krista plays the role of peacekeeper the way she did thirty years earlier.

Soon, a murder disturbs the quiet of the summer homes that dot the isolated cove. Deborah's suspicions follow her like the Maine landscape-plenty of sunshine, plenty of fog, and plenty of evening mosquitoes that, like the questions now plaguing their reunion, arrive like the sparks of fireworks. Where is Brenda's husband? Where have her caretaker and cook gone? Who is the thin young man who keeps appearing? Is one of them a murderer? Or could it be the old woman who lives across the street; her son, who runs an oyster farm in the face of global warming; or the poet-tenant who lives in her apartment? Deborah even suspects each of the friends she grew up with. Her idyllic summer retreat has turned as deadly as contaminated shellfish. Will she find the answers before it's time to leave Calderwood Cove?