Cruel Capers on the Caribbean — Kassandra Lamb

Trouble seems to find Kate Huntington, even on a Caribbean cruise. She and her friend, Liz, befriend socialite Cora Beall, who is having relationship problems. When Cora is found dead, her cabin locked from the inside, the ship's captain assumes it's a suicide.

Kate is skeptical. Her private detective husband begs her to let it go, but the evidence points more and more toward murder. And she can't stop thinking about Cora's teenage daughter who is back in the States with her stepfather. Which is worse, thinking your mother committed suicide or being raised by her killer? Or is Cora's seemingly-innocent, screenwriter boyfriend the real murderer?

And the toughest question of all... how did Cora's killer get out of a locked room?

This is the second of the Kate on Vacation novellas, a parallel series to the Kate Huntington mysteries.