The Stowaway(1978)

The Stowaway is a sci-fi thriller that traps five crew members aboard a spacecraft with a deadly secret. When an alien entity kills one of them and replaces the victim with an identical copy, paranoia spreads through the ship. No one knows who among them is the imposter—or what the creature wants. As suspicion turns crew against crew, the survivors must figure out which of their own has been replaced before the alien picks them off one by one. The tension mounts as trust becomes impossible and every interaction feels like a potential threat. With limited resources and nowhere to run, the remaining crew races to identify the stowaway before it's too late.