Ralph Leslie, a young doctor, is recovering from a bout of Typhoid. Partly to earn some money and partly to stay close to a girl he has espied through his hospital window, he gets a job on board a yacht named Ella. What promised to be a tranquil voyage soon turns into a nightmare as three of Ella's passengers are found hacked in to pieces. With land nowhere in sight, the crew of Ella do all they can to reach the nearest port before the unknown assailant strikes again.