Slack Tide — George Harmon Coxe

A marina owner gets caught up in a murder investigation

The girl in the water is unfamiliar to Don MacLaren. This is odd since, as the owner of the island's only boat dock, he knows everyone who steps foot on the small spit of land. He hoists the young swimmer out, and is helping her get warm when Oliver Kingsley, the island's wealthiest citizen, comes to collect her, claiming he's her husband. The girl refuses to leave with Kingsley, resulting in a brawl between the two men.

In the morning Kingsley is found dead, and after the cops learn about the fight, they peg MacLaren as their chief suspect. As MacLaren struggles to understand the mystery behind the rich man's death, he finds that even the smallest island can hold deep secrets.