It is December 1875 and the recently established Railway Constabulary is faced with its first murder case. Sergeant Sam Spray is in charge and along with his assistant Constable William Archer they explore the railways, canals and wild country of the White Peak. The many twists and turns of the case are complicated by the reserved sergeant’s emotional entanglement with his landlady, the cool Elizabeth (Lizzie) Oldroyd. The case’s solution and Sam’s relationship with Lizzie turn out to be uncomfortably connected.