Unless a case is elucidated within a day or two of the commission of an offence the first hot pursuit resolves itself into a dogged, wearisome but untiring watchfulness on the part of the C.I.D. A case is never abandoned while there remains a chance, however slight, of running a criminal to earth. And even when the detectives, like hounds baffled at a scent, are called off, there remains the gambler's element of luck. Even if the man who had original charge of the case should be dead when some new element re-opens an inquiry, the result of his work is always available, stored away in the Registry at Scotland Yard. There are statements, reports, conclusions--the case complete up to the moment he left it. The precaution is a useful one. A death-bed confession may implicate confederates, accomplices may quarrel, a jealous woman may give information. There have been unsolved mysteries, but no man may say when a crime is unsolvable. Heldon Foyle had many avenues of information when it was a matter of ordinary professional crime. The old catchword, "Honour among thieves," was one he had little reason to believe in. There was always a trickle of information into headquarters by subterranean ways. The commonplaces of crime were effectively looked after. Murders are the exception in criminal investigation work, and while other crimes may be dealt with by certain predetermined if elastic rules, homicide had to be considered differently. Yet Foyle had cause to think that there might be little harm in setting to work the underground agencies which at first sight seemed to have little enough in common with the mystery of the rich Robert Grell. These spies and informers would try to cheat and trick him. Some of them might succeed. It would cost money, but money that might not be wasted. Four of the five chief detective-inspectors who form the general staff of the C.I.D. were in the room, among them Wagnell, who had passed a quarter of a century in the East End and knew the lower grades of "crooks" thoroughly, collectively, and individually. Foyle shut the door. "I wish some of you would pass the word among our people that we will pay pretty handsomely for any one who puts us on to the gang mixed up in this Grell business. Word it differently to that. You'll know how to put it. You might get hold of Sheeny Foster, Wagnell, or Poodle Murphy, or Buck Taylor. They may be able to nose out something." "Buck was sent up for six months for jumping on his wife," said Wagnell. "I haven't seen Sheeny lately, but I'll try to get hold of him, and I'll have the word passed along." So, having made the first step in enlisting a new and formidable force of guerillas on the side of the law, Foyle went back to his office to revolve the problem in his brain once more.