Yachts and Yelps

Fenella Woods and her niece, Margaret, are surprised to find visitors waiting for them at their luxury apartment building when they return home from a walk. Thornton DeVries had been friends with Fenella's aunt, Mona, and was unaware that she'd passed away. He's just arrived on the island on a luxury yacht, accompanied by family and friends. They have a short conversation and agree to have dinner together the following evening.
Later that night, though, Fenella and Margaret stumble across a dead body. One of Thornton's traveling companions has been murdered and everyone on board his luxury yacht is a suspect. Meanwhile, Margaret is trying to find a job, and Fenella and her fiancé, Daniel, are talking seriously about setting a wedding date.
Margaret is determined to work out what happened to poor Delia Reid. With help from Mona's ghost, who keeps interfering in the investigation, she and Fenella find themselves learning all about Thornton, his former wife, and their associates. But is that knowledge enough to help them determine who killed Delia before someone else ends up dead?