On the secluded Isle of Jersey in the final days of World War II, a young woman waits in vain for her beloved husband to return from the front. Grace has been raising her two young children alone in her beautiful, cavernous Victorian mansion, the one place she believes them to be safe. But they are not safe. Not anymore.

When a new trio of servants arrives to replace the crew that inexplicably disappeared, startling events begin to unfold. Grace's daughter reveals she has been communicating with unexplained apparitions that come and go in every room of the house. At first, Grace refuses to believe in her children's scary sightings, but soon, she too begins to sense that intruders are at large. Who are these numinous trespassers? And what do they want from Grace's family?

In order to discover the truth, Grace must abandon all of her fears and beliefs and enter the otherworldly heart of the supernatural.