Summer, 1941. As London is devastated by the Blitz, the National Gallery's most precious paintings find a new sanctuary in the slate mines of north Wales, supervised by Detective Chief Inspector Archie Penrose. Vacationing in the area is Josephine Tey, as well as Noel Coward who is preparing his defiant new play, Blithe Spirit, in which Margaret Rutherford plays a clairvoyant. When a woman's grave is discovered amid the debris of a roof fall in the mines, Archie and Josephine are plunged into a forty-year-old mystery, and a death that threatens to tear apart the close-knit Welsh community. Secrets begin to emerge, and no-one is immune to the voices of the dead.