Blind Barber — John Dickson Carr

The bunk's mattress was soaked with blood. The old-fashioned razor was folded shut.
But it had been recently used. It was smeared with blood.
A voice broke the terrible stillness in the stateroom:

"THE BLIND BARBER HAS BEEN HERE TONIGHT!"

On an Atlantic crossing of the good ship Queen Victoria, a vicious killer is loose, and four high-living characters are hellbent to pin him down. Dr. Gideon Fell soon finds himself up to his chins in misadventure as he wades into a comedy of terrors that boasts a reel of compromising film, an emerald elephant, and a lethal razor for props, murder as the evil deed, and unmitigated mayhem as the comedy relief.