This paganistic, gothic horror thriller is quite a tense and at times exhilarating film that goes in some surprising and quite unexpected directions. The first hour is built as a potential Wicker Man scenario but it then moves into something much more interesting and shocking. Set in 1905 and opium addicted Thomas (Dan Stevens), who is nursing some inner demons from his past, is implored by his wealthy father to rescue his sister from the clutches of a weird religious community that inhabit an isolated island. Pretending to be a convert he joins the sect to try and find her. The community run by Malcolm (Michael Sheen) suspects there's an interloper and they have a very dark secret to hide. Not a film for the faint hearted as this has torture, gore and bloody violence. But it's quite enthralling and has the style and feel of a Hammer horror film such as Die Monster, Die (1965) for instance. The island's location isn't specified but it's like a lush, forested place that hides some dark force. The support cast are excellent including Lucy Boynton and Mark Lewis Jones especially. The film exudes elements of originality making it a compelling watch and whilst it's open to different readings and fans will spot the influences it's definitely one to check out.