Echoing others here, a strong cast with a promising and tension-building first half is really let down by a slightly disappointing second half and a rather ridiculous final scene, in my opinion.

Unfortunately, [spoiler]when the enemies start revealing their faces, it becomes a little less scary for some reason. Adding to the poorer quality of the backend of the film is the fact that the film's lead character, Harper, suddenly becomes almost superhuman: she carries on fleeing after being shotgunned in the shoulder, standing on some large nails, and having the palms of her hands ripped off my industrial-strength superglue, like as if nothing happened! She also seems to suddenly change her entire personality, from shy and timid to a confident ass kicker[/spoiler].

That said, the first act is a solid 8/10 but the second is more like a 4/10, which was a shame. Nevertheless, it's a more than enjoyable watch overall.