The Retreat

 by Sarah Pearse

This book seems to reflect some of an Agatha Christie vibe.

A police officer, who is recovering from PTSD, is sent to an island to investigate an accident/murder.  The island had a violent past.  The island has a huge rock formation that looks like the grim reaper.  Some students on a school trip were murdered there.  However now the island is home to a luxury resort designed by the police officer's boyfriend.

When she arrives, with a colleague, she discovers her boyfriends sister is the Manager of the resort.  I don't think she knew this.  The incident they are investigating is the death of a woman.  It appears she fell over a glass wall to rocks below.  It first seems an accident.  However, upon further investigation it is determined to be murder.

The officer finds out that family of the woman, and their boyfriends as well as her boyfriend are on the island but the woman was not supposed to come -- too busy at work.  She did not tell them she changed her mind.  Shortly after another member of that group, the son of the man who owns the island is found drowned.  He had been diving and was an experienced diver.  Now tension escalates.  The police officer asks for more support but is told other staff are busy on another serious crime(s) so she and her partner are on their own.   Some guests leaves after the second death, the others are gathered into a central area in the resort.  The police officer's boyfriend arrives and he gets angry when she questions his sister, their relationship seems on the edge.  At one point the boyfriend's sister disappears, she has been kidnapped and left to die by the murderer.  The police officer finds her and saves her.

In the end we find out one of the "family" group is the murderer.  He wants to avenge? his father who was imprisoned for murdering the young people years before.  He is angry the island was turned into a resort rather than designated a nature sanctuary.

This was an okay mystery and kept one guessing except it was hard to keep everyone straight with so many characters in the book.