It's June on Cape Cod and that means tourists, but a murder is about to cast a shadow over the sunny season—and over bike shop owner Mackenzie "Mac" Almeda's Cozy Capers Book Group . . .

With tourist season about to begin, the Friends of the Lighthouse organization is looking for a new tour guide for the now vacant decommissioned lighthouse. They hire Jessica Goodwell, a woman Mac's mother, Astra, met in town. When Jessica doesn't show up to give a scheduled tour on the summer solstice, Derrick, the former tenant and Mac's half-brother, agrees to do it. But when he arrives, he's shocked to find Jessica's lifeless body, and he quickly calls Mac . . .

Mac advises Derrick to call the police. She fears he might become a murder suspect—it wouldn't be the first time—though Derrick says he's never seen the victim before. But when the Cozy Capers gather to discuss the crime, it turns out there's someone else to worry about. Book Group member Zane King is Jessica's cousin and is soon called in for questioning as a person of interest.

As usual, law enforcement doesn't want the Capers butting into the case. But they have ideas of their own, especially when they learn that Jessica was digging into the truth about her own mother's murder, fifty years before. Soon, with the help of the mystery author the Capers are currently reading, plus Jessica's niece who happens to be an investigator reporter, the Capers have their own list of intriguing suspects. Only one thing is certain: someone is willing to kill to keep a half-century old secret in the dark . . .