Undercurrent

During a voyage from Vancouver to San Francisco, a passenger on the SS Java Queen becomes suspicious of a man posing as another passenger, Mr. Ashcroft. After overhearing a conversation, it's revealed that the ship's captain and crew are involved in smuggling aliens into the US. Following a plan to cover up a murder and claim an inheritance, the passenger orchestrates a hit-and-run to fake the death of Ashcroft. However, the passenger's scheme is foiled when they are confronted by an investigator, who was trailing them from the ship. The truth behind the murder and the smuggling operation is uncovered, leaving the passenger's plans in shambles.