Sixteen-year-old Libby returns from summer camp to the surprise introduction of her Mum's chiselled fiancée, John Smith, who emerges from the backyard lake. When John ignites an inappropriate curiosity in Libby her suspicions are escalated when, one night, she wakes to a piercing, amber light from the depths of the lake outside. She spots John on the shore, basking in the luminance, until he walks into the water, completely submerges and then.... disappears. Libby quickly uncovers his true nature and sinister motive, but will she be able to protect her Mother who clings to his infectious charm.