The 39 Cupcakes (Movie Club Mysteries, Book 4)

Police Sergeant Reynolds sighed. "Of course he was murdered, Maggie. You''re in the vicinity."
"A low blow," I said indignantly. "Before today, I hadn''t found a dead body in six weeks. And this is just a head."
Ex-cop-turned-P.I. Maggie Doyle is stuck chaperoning a group of bratty summer camp kids to an archaeological dig on Whisper Island. After a day of fart jokes, fidget spinners, and fist fights, Maggie''s regretting volunteering-and then one of her feral charges discovers a skeleton.
At first it looks like a cold case, but the situation takes a sinister turn when a member of the excavation team winds up dead. Maggie is determined to get to the bottom of the mystery before more bodies stack up. With her police officer boyfriend on vacation, his nitwitted fellow officer is what passes for law and order on the island. Now if only she can dodge the bumbling Sergeant O''Shea...