Set in post-war Britain, ten year-old Lewis Aldridge is grief-stricken as he struggles to cope with the death of his beloved mother. Left under the care of his emotionally distant father Gilbert, whom he barely knows and who quickly remarries, Lewis is forced to bury his feelings.

A dysfunctional family awake on Christmas morning to discover they’re sealed inside their house by a mysterious black substance. On television, a single line of text reads: “Stay Indoors and Await Further Instructions.”