Revenge of the Haunted Souls (1939)

On a stormy night, a rich man is murdered, doused in acid and dumped at sea. Luckily, the young wife of the rich man is helped by an old knight-errant who has been in hiding for many years to track down the murderer. It turns out that the murderer is a longtime friend of the rich man, and he has killed him because of his greed.