Watch Undertow Full Movie Free Online 123Movies. After his car breaks down, Jack seeks shelter, lost in a thunderstorm in a remote shack in the woods. He finds himself held at gunpoint by a deranged mountain man who lives there with his young wife. As the storm rages on, tension mounts in the small cabin. Matters reach a climax when Jack falls for the beautiful woman and tries persuading her to escape with him. Soon, the situation escalates into deadly violence...