Harry is on a train returning from Edinburgh to London. He gets into conversation with a fellow traveller. This man is the poetic Shadbolt, but there is something about him that Harry cannot possibly know. Shadbolt is also a professional assassin and his presence on the train is no coincidence. He has been paid to kill Harry at a given time, a fact to which Harry must tumble for the ultimate show-down.
—don @ minifie-1