In 1854, young silversmith Hugh Kellow leaves Paddington for Cardiff carrying a valuable silver coffee pot modelled as a locomotive. He talks too freely about the object to two interested passengers, and his journey ends with his body discovered at the Cardiff Railway Hotel beside an emptied valise.
Inspector Robert Colbeck and Sergeant Victor Leeming investigate both the murder and the disappearance of the silver masterpiece. The trail leads through railway hotels, workshops and competing claims to the object, where the identity of the thief may not be the same as that of the killer.