Katie is almost six. She's very much looking forward to her birthday party, with her mum Leanne and sister Chloe and of course her very best friend, JoJo.

Grace has no daughter, no mum, no family, but she loves her friends next door, perhaps especially Katie, since she has no child of her own.

It's a good life. It's enough. So when Grace begins to see things that can't possibly be there, strange visions that seem to portend something happening to those she cares about, it's a mother's love she feels. A mother's rage. A mother's determination to protect them . . .