Chief Inspector Heldon Foyle is confronted with the most bewildering case of his career when Harry Goldenburg, the notorious crook, is found foully murdered in the Grosvenor flat of the American millionaire Robert Grell. Here is what appears to be a perfect crime without a single clue to lead anywhere. But the investigation has barely started when Foyle makes an astonishing discovery that sets him on the trail of an arch-criminal who will test the determination of Scotland Yard to its limits and require all the ingenuity of modern detective work at their disposal to solve the case.

First published in 1913, The Grell Mystery is one of the earliest and most authentic 'police procedural' novels, having the rare distinction of being written by a real Metropolitan Police detective, Frank Froest, who was a household name for solving some of the country's most high-profile crimes.