An exquisitely designed silver coffee-pot in the shape of a locomotive is on its way to Cardiff in the care of the young, talented silversmith, Hugh Kellow. It has been commissioned by wealthy ironmaster Clifford Tomkins for his acquisitive wife, who wants it to be the envy of all her friends -- and enemies.

But the coffee-pot is stolen. When a gruesome murder is committed at the Railway Hotel, Winifred Tomkins is distraught. Caring little for the dead silversmith, all she can think about is her missing treasure. Inspector Colbeck and Sergeant Leeming of the Detective Department are summoned to Wales from London by telegraph and they are soon confronted by some additional crimes. The situation is complicated by the arrival of a famous theatre company and by revelations of illicit liaisons among members of the local high society. There is no shortage of suspects and Colbeck has to sift through layers of deceit to find the killer -- before it is too late.