In UK cinemas from 23 November

The internal logic of the horror film is a curious thing: the idea that a bunch of college kids might fly all the way from America to Ireland just to pick some magic mushrooms is stupidly implausible, yet their consequent bloody dispatch makes perfect sense.

That aside, Shrooms has some fairly fundamental flaws. Its horror factor is undermined by the fact that we can’t linger over the teens’ deaths, as we aren’t supposed to know whether they’re victims of something real or supernatural, or just on one hell of a bad trip. Although the trip doesn’t seem that bad. The mushrooms should be the crux of the film, and the characters talk about them a lot, but it’s soon apparent that people really are dying, and there’s little to suggest that they’re doing much hallucinating: there’s a bit of double vision when looking at trees, and a talking cow, and then the effects seem to wear off. Admittedly, however, this is difficult to establish because the viewpoint keeps shifting, as represented by an æsthetically awkward jumble of looks, mostly Blair Witch, Asian Horror and insipidly druggy visuals. All of which precludes audience involvement, as do the vapid, unsympathetic characters (Jack Huston, in particular, is miscast in a role that requires a stronger, more charismatic actor), clichés (forest, Deliverance-style inbreds, abandoned institutional building and so on… ), and distracting continuity errors.

Despite these irritations, Shrooms is a moderately enjoyable film, with some good-looking moments. Had its makers steered clear of derivative genre parody, given their characters some depth, worked up some scares and unified the film with a more hallucinogenic look, it might even have been the psychological thriller they were aiming for.