A thief is loose aboard HMS Queen Victoria, and four amateur detectives are hell-bent on tracking him down. Unprepared for the evidence that their sleuthing activities will uncover - a reel of compromising film, a blood-soaked stateroom bunk, a lethally sharp razor and an emerald elephant - they find themselves sinking deeper into misadventure and pandemonium.

But when the boat arrives in Southampton harbour, another passenger, mystery writer Henry Morgan, calls in the famous Dr Gideon Fell - who identifies sixteen clues that lead him to the murderer.