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.

His thoughts wandered to Sir Ralph Fairfield. Here was a man whose services would be invaluable if he could be persuaded to help. Grell knew him; trusted him. Foyle was a man who never neglected the remotest chances. He deemed it worth trying. True, so far as their encounters were concerned, Fairfield had not been encouraging. He would probably need delicate handling. Foyle wrote a note, scrutinised it rapidly, and, going out, gave it to a clerk to be sent at once by special messenger.

"Mr. Heldon Foyle presents his compliments to Sir Ralph Fairfield and would be obliged if he could see him at his office at six o'clock this evening, or failing that, by an early appointment, on a matter of urgent importance."

That was all it said: Foyle never wasted a word.

At five minutes past six that evening, Sir Ralph Fairfield was announced. He ignored the offer of a chair which was made by the superintendent, and stood with stony face a few paces from the door. Foyle was too wise to offer his hand. He knew it would not be accepted. He nodded affably.

"Good evening, Sir Ralph. I was hoping you would come. I would not have troubled you but that I felt you would like to know how we are getting on. You were a friend of Mr. Grell's."

"Well?" said Sir Ralph frigidly. "I am here, Mr. Foyle. Will you let me know what you want to say and have done with it?"

His manner was entirely antagonistic. There was still a lingering fear of arrest in his mind, but his attitude was in the main caused by the fact that he believed he had been suspected by the other. The superintendent partly guessed what was passing in his mind.

"I want your word first, Sir Ralph, that what I tell you shall not be spoken of by you to any living soul," he said. "Then I will tell you frankly and openly the whole history of our investigation, and you can decide whether you will help us or not. No—wait a moment. I know how loyal a friend you were of Robert Grell's, and it's in the light of that, that I am going to trust you. He is not dead. He is in hiding. It is for you to say whether you will help us to find him. If he is innocent he has nothing to fear."

He was watching the other closely while he sprung the fact that Grell was alive upon him. He wanted to know whether it was really a surprise, whether in spite of the vigilance of the C.I.D. men Grell or his companions had managed to communicate with Fairfield. The baronet had opened his mouth to speak. A flicker of colour came and went in his pale cheeks, and he fingered his stick nervously. Then his jaw set, and he strode to where the superintendent was sitting and clutched him tightly by the arm.

"What's all this?" he demanded hoarsely. "Do you mean to say Grell is not dead?"

"As far as I know he is as alive as you or I at this present minute," said Foyle. "If you want to hear about it all, give me your word and sit down. You're hurting my arm."

"I beg your pardon," said the baronet mechanically, and, stepping back, seated himself in a big arm-chair that flanked the desk. He passed his hand in a dazed fashion across his forehead and his composure came back to him. Staggering, incredible as the statement seemed, there was that in Foyle's quiet tones that gave it the stamp of truth.

"Of course, I'll give you my word," he said.

Foyle was satisfied that the baronet knew nothing. There was a deeper policy behind the pledge he had exacted than that of preventing a leakage of confidence. Fairfield would not go behind his word. In that the superintendent had judged him accurately. But the pledge would also tie his hands should Grell or his companions eventually manage to communicate with him. Even if he decided not to help the police, he would find it difficult, without going behind his word, to assist the missing explorer.

From the beginning he traced the trend of the investigation, Fairfield leaning forward and listening attentively, his lips tight pressed. As Foyle brought out the points, the baronet now and again jerked his head in understanding. The detective slurred nothing, not even the accusation and resolve of the Lady Eileen Meredith. The baronet choked a little.

"You think she really meant to kill me?" He waved his hand impatiently as Foyle nodded. "Never mind that. Go on. Go on."

Foyle finished his recapitulation. Sir Ralph's eyes were fixed on a "Vanity Fair" cartoon of the Commissioner of Police hanging framed on the wall. He was trying to readjust his thoughts. From a man who believed himself under deadly suspicion he had suddenly become a confidant of Scotland Yard. He had been released of all fear for himself. And Bob Grell was alive after all; that, he reflected, was the queer thing. What did it mean? Where was the reason for this extraordinary tangle of complications? Grell always was deep, but, so far as his friend knew, he was a man strictly honourable. How had he come to be involved in an affair that looked so black against him? There was Eileen to be considered too. In spite of himself, he could readily believe the story of the pistol. She had believed him guilty of the murder. Her mood when last he saw her had been that of a woman who would stoop to anything to compass her vengeance. But she knew he was not guilty now. That might make a difference to his course of action. Should he throw in his lot with Foyle and assist in bringing Grell within the reach of the law?

"What do you say, Sir Ralph? Will you help us?"

Foyle's suave voice broke in upon the thread of his thoughts.

He shook himself a little and met the detective's steady gaze.

"If I do, will it mean that you will arrest Grell for murder?"

The superintendent caressed his chin and hesitated a little before replying.

"I have been quite open with you, Sir Ralph. I don't know. As things are at present, it looks uncommonly as though he had a hand in it. He is the only person who can clear himself. While he remains in hiding everything looks black against him. We have managed to keep things quiet until the resumption of the inquest. When that takes place we shall not be able to maintain the confusion of identity. With things as they stand, the jury are practically certain to return a verdict of murder against him. If he is not guilty, his best chance is for us to find him. Understand me, Sir Ralph. If he is innocent you are doing him no service by refraining from helping us. Every day makes things blacker. If he is guilty—well, it is for you to judge whether you will shield a murderer even if he is your friend."

To another person, Foyle would have used another method of persuasion, talking more but saying less. He had staked much on his estimate of the baronet's character, and awaited his reply with an anxiety of which his face gave no trace. Very rare were the occasions on which he had told so much of an unfinished investigation to another person, and that person not an official of Scotland Yard. Often he had feigned to open his heart with the same object—to win confidence by apparent confidence. The difference now was that he had given the facts without concealment or suppression.

Fairfield fingered his watch-chain, and the big office clock loudly ticked five minutes away.

"I will assist you as far as I can, but you must allow me to decide when to remain neutral," he said at last.

"Agreed," said Foyle, and the two shook hands on the bargain.