A Failure of Nerve
This could have been a fantastic movie if the producers just hadn’t chickened out in the end. Think how great it would have been if Gallagher had opened his mouth and a disgusting parasite had come out and entered into Beck’s mouth. We would have been forced to think that something that looks like a combination slug-insect could be good and kind.
It is so standard in science fiction movies that good aliens look like humans, usually with frail bodies, slightly larger craniums, and larger eyes. But if the aliens look like insects, then we know they are evil and must be destroyed.
This movie could have split those alien stereotypes wide open, making us accept what we should have known all along, that someone who is ugly may nevertheless be good. But there was a failure of nerve. Sure, we can assume that Gallagher and his nemesis were of two different species. We can make up any story we want. But the result is still the same. The minute Gallagher opened his mouth and a beam of yellow light came out instead, this movie became second rate.