The Starboard Knife — Ernie Lindsey

Ten friends. Two days on a twenty-five-million-dollar yacht, far from shore. Alcohol, sun, skin, and loosened inhibitions. What they find after a night of drunken debauchery is both senseless and horrifying; so much blood, a missing knife.

Everyone's a suspect. Everyone claims to be innocent. Everyone quickly learns what happens when you keep your friends close, and your enemies closer.