Quiet and polite, obsessively neat, clean and tidy, eight-year-old Tom is unlike any child Maggie has ever fostered before. Tom has been taken into care following concerns that his dad is struggling to cope after the death of Tom's mum. At first, Maggie doesn't know what to make of this shy, nervous little boy who never cries and is terrified of getting dirty. But as Tom's cleaning rituals start to get more extreme, Maggie fears that there's something more sinister going on beneath the surface.