The Intruder (1975)

"Who - or what - is the intruder? One thing is for certain: it will not stop until it kills them all."

The lust for gold and the reading of a will brings eleven visitors to a remote island retreat, but an unseen, seemingly unstoppable evil follows to stalk them one by one. The bodies don't stop dropping until the final shattering conclusion. Who - or what - is the intruder? One thing is for certain: it will not stop until it kills them all.