December 1864. As a cold winter wind scours the Worcestershire countryside, an excursion train comes through a tunnel in the Malvern Hills to be confronted by a blockage on the line ahead. Although a disastrous derailment is averted, the passengers are alarmed.

Cyril Hubbleday, the man in charge of the excursion, alights to investigate further, but the angry altercation with the driver is cut short by a shot from a sniper, straight through Hubbleday's head. Christmas is coming all too soon and Inspector Robert Colbeck and Sergeant Victor Leeming are under pressure to solve the case quickly. However, with enemies in the shadows behind the seasonal trip, and with strong criticism from the local constabulary, the hunt for a cold-blooded killer is far from straightforward.