The railway viaduct

As a train speeds over the Sankey Viaduct, the dead body of a man is hurled into the canal below. Inspector Robert Colbeck and Sergeant Victor Leeming take on the most difficult case they have yet faced. Hampered by the fact that the corpse has nothing on him to indicate his identity, they are baffled until a young woman comes forward to explain that the murder victim, Gaston Chabal, is an engineer, working on a major rail link in France. As the case takes on an international dimension, problems accumulate.