The famous detective Sir Charles Foxworth is taking a holiday on the Mississippi with his servant Regis on the Delta Princess. He's just taking a stroll around the upper deck of the ship when he discovers an open cabin door. Behind it: a dead man. As it turns out, the body of Raleigh Cartwright III. Sir Charles has three days to find the murderer, because then, the ship will reach New Orleans, giving the culprit a safe chance to escape.