Why do the Pit-Prop Syndicate stealthily change the numbers on their lorries? This question leads Merriman to discover that things aren't as they seem at the logging company he stumbles across while motorcycling through France. His fears for the manager's daughter ,Madeleine Coburn, bring him back to investigate with his friend Hilliard.
Later, when a death confirms their suspicions of criminal activity, Inspector Willis of Scotland Yard takes up the investigation and using police procedure finally solves the mystery of the lorry numbers.
Freeman Wills Crofts (1 June 1879 – 11 April 1957) was an Irish mystery author, best remembered for the character of Inspector Joseph French. A railway engineer by training, Crofts introduced railway themes into many of his stories, which were notable for their intricate planning. Although outshone by Agatha Christie, Raymond Chandler and other more celebrated authors from the golden age of detective fiction, he was highly esteemed by those authors, and many of his books are still in print.