A rather enjoyable debut from a director who seems to have a sincere fondness for horror films of a bygone era. In this fairly simple storyline (a murder mystery that turns into a monster movie), film buffs will find a hodge-podge of references to many genre classics, like Dario Argento's thrillers of the 70s or English Hammer films (in particular John Gilling's Plague of the Zombies for its ritual scenes), and even to stranger oddities like Jack Arnold's "Monster on the Campus" or the Avengers British TV series. Add a bit of Celtic mythology for a background, some fight scenes, and stir well... Now mixing all this into a pleasant, if air-headed, B-movie makes for an interesting challenge! It doesn't always succeeds but is certainly better than other French genre efforts in the field. The direction is often stylish and the performers have fresh faces, the music score is quite good.
Of course this is a low budget production (it probably didn't cost more than a couple million dollars), and does suffer from it: several scenes could have been helped by better production values. And there are a few plot holes and a couple of long stretches. But it finally wins the day by retaining its charm to the end just out of sheer unpretentiousness. Not so common a feat, these days.