Charlie and James are just starting their lives together; young and in love, they're relishing having no responsibilities, until Charlie discovers that she is pregnant. In a moment of youthful abandon, they decide to keep the baby. Into their world comes Thea, a beautiful little girl. But her arrival brings with it terrifying entities that threaten their newly formed family, things that are beyond their understanding. Panic stricken, the young parents enlist the help of James' estranged father Alistair, a dilapidated would-be occultist whose obsession drove his family apart and led his son to despise him. He diagnoses Thea as a beacon - a child whose very presence attracts the attention of the supernatural creatures that surround us. Charlie and James realise that they must dedicate their lives to protecting their unplanned daughter.