The Postmaster looked over my shoulder. As I turned to look I saw a flicker of movement from across the street. I felt unseen eyes peer at me.
He walked away without another word. I watched as he climbed onto his bicycle and sped away down the street. I turned back and looked over my shoulder.
Someone had been watching us.

1904. Thomas Bexley, one of the first forensic photographers, is called to the sleepy and remote Welsh village of Dinas Powys, several miles down the coast from the thriving port of Cardiff. A young girl by the name of Betsan Tilny has been found murdered in the woodland - her body bound and horribly burnt. But the crime scene appears to have been staged, and worse still: the locals are reluctant to help.

As the strange case unfolds, Thomas senses a growing presence watching him, and try as he may, the villagers seem intent on keeping their secret. Then one night, in the grip of a fever, he develops the photographic plates from the crime scene in a makeshift darkroom in the cellar of his lodgings. There, he finds a face dimly visible in the photographs; a face hovering around the body of the dead girl - the face of Betsan Tilny.