1866. On a dark, brooding summer's evening, Agnes Lenham seats herself in an empty first-class compartment on the train to Portsmouth. She is joined by a naval officer and a middle-aged man, in high spirits after dining at his club, travelling to his home on the Isle of Wight. His name is Giles Blanchard - and within moments of the train leaving the station, the sailor strangles him... At Scotland Yard, Detective Inspector Colbeck and Sergeant Leeming...

"1862. A goods train is going through the Sapperton Tunnel when it hits a makeshift pen of sheep inexplicably set up near the exit. The animals are slaughtered by the impact whilst the train hits a pile of rocks and is derailed, seriously injuring the occupants. Inspector Colbeck is called in to investigate and discovers that the shepherd and his dog are missing. Stephen Ryle who owned the sheep is shocked by the occurrence which further affects him...

1861, East Anglia. Alone in a first-class carriage, the Swarbricks are robbed at gunpoint, but when the universally-admired Swarbrick fights back, the train robber takes more than money and jewellery, killing the man working to unify East Anglia's tangle of railway networks. Inspector Colbeck is brought in from London, as the only detective in Britain with enough expertise for the job. But as Swarbrick's glowing reputation begins to crumble, the line...