Death walks a fog-shrouded island. The pretty young girl called Sister sees Tom, the man she secretly loves, pulling a woman's body from the water--or is he dumping it?--while holding a hammer in his hand. No, she's certain that Tom would never kill. But if they report the death as a murder, Sister's testimony will surely make Tom the top suspect.
At the urging of their adoptive father and his lawyer, Tom agrees to present the death as a tragic accident and marry Sister so she can't be forced to witness against him. But the unknown killer is still out there, and Sister saw something that she doesn't realize is significant. As she tries to figure out who the murderer is, the murderer moves to strike again...