John Constantine (Keanu Reeves) is a private investigator who believes in things that go bump in the night -- which makes him somewhat of an eccentric in a world ruled primarily by logic. So, it comes as a surprise to him when a female cop (Rachel Weisz) seeks his counsel after her twin sister dies in what first appears to be a suicide. She wants definitive proof of the cause of death … but the answers may only come with blind faith on her part.