Within the invisible cordon that Foyle had drawn about Grell's house in Grosvenor Gardens, Dutch Fred loitered, his keen, ferret eyes wandering alertly over passers-by. Misgivings had assailed him during a vigil that had lasted several hours. It was all very well to be "in with" the police; but suppose their plans miscarried? Suppose Red Ike and his unknown friends got to know that the "double cross" was being put on them? Fred fingered a heavy knuckle-duster in his pocket nervously. Man to man, he was not afraid of Ike, but there were his friends.

The tall straight figure of Heldon Foyle, with coat collar turned high up, had passed him once without sign of recognition and vanished in the enveloping shadow of the slight fog that confused the night. Yet, though the superintendent had apparently paid no heed, he was entirely alert, and he had not failed to observe Freddy. What he wanted was to see who else was in the street. He returned by a detour to an hotel in the Buckingham Palace Road, outside which a big motor-car was at rest, with a fairly complete mental picture of three people who might be possible spies among those he had passed.

The thickening fog was both an advantage and a disadvantage to the detectives—an advantage because it would force any person watching on behalf of Grell and his associates to keep within a reasonable distance of the house if Ike was not to be lost sight of, and a disadvantage because it would afford increased facilities for any one to slip away.

To Green, seated in the motor-car, Foyle commented on this fact.

"You'll have to have your breakdown rather closer to the house than we thought," he said. "Give Ike a good chance inside. You've got the duplicate key all right?"

"That's safe enough," answered Green, tapping his pocket. "If I don't see you after we've bagged him I'd better charge him with housebreaking, I suppose?"

"Certainly. Now get along. It's a quarter to eight."

The car moved silently forward and took the corner of Grosvenor Gardens. Thirty paces beyond the spot where Dutch Freddy was lighting a cigarette it came to a stop, while the chauffeur, dropping to the ground, rummaged fiercely with the interior. Green leaned back in the shadow, his eyes fixed on the steps leading to Grell's house. There was a sufficient air of plausibility about the whole accident to impress any one but the most suspicious.

Heldon Foyle had entered the hotel, for he did not care to run the risk of frightening his quarry by showing himself again until it was necessary. But he kept a vigilant eye on the clock. Promptly as the hands touched ten minutes past eight he made his way once more to the corner of Grosvenor Gardens. A labourer, with corduroy trousers tied about the knee and a grimy, spotted blue handkerchief about his neck, approached him with unlit pipe and a request for a match.

"Red Ike's gone along," he said, as Foyle supplied him. "Nobody else has been hanging round except Freddy. The constable on the beat passed along just after Ike."

The match, was dropped in the gutter, and the superintendent, his face set grimly, moved slowly on. The labourer crossed to the other side of the road and followed. Foyle was quite near the house when Green walked up, accompanied by his chauffeur, and made quickly up the steps. Shadowy in the fog, the superintendent could see the dim outline of a constable's uniform. The man was peering anxiously at the doorway through which Green had gone.

"Well, my man," said Foyle sharply, "are you on duty here? Who are those people who have just gone in there?"

The policeman gave a barely perceptible start, and then took a pace forward.

"I—I believe they have no right there. I must go and see," he said, but was brought up with a jerk as Foyle's hand clutched his wrist. The labourer who had wanted a light was coming across the road at a run and, though a little puzzled, had seized the constable's other hand.

"No, you don't," said Foyle peremptorily. "When you masquerade as a policeman again, my friend, make sure you have a letter of the right division on your collar. This district is B, not M. I am a police officer, and I shall arrest you on a charge of being concerned in an attempt at housebreaking. You'd better not make a fuss. Come on, Smithers. Let's get him into the car."

The prisoner made no resistance. He seemed dazed. Once in the car, the detective took the precaution to handcuff him to his subordinate—right wrist to the officer's left wrist—for he did not know how long the wait for Green might be, and it seemed wisest not to run risks. Detectives rarely handcuff their prisoners unless travelling. It is conspicuous and unnecessary.

"Now we're more comfortable," said Foyle, sinking into the cushions of the car. "If you want to give any explanation before I formally charge you, you may. Only don't forget that anything you say may be used in evidence against you."

"Is it an offence to go to a fancy-dress ball in a police officer's uniform?" asked the prisoner. "Because if it is, I shall plead guilty."

"You can make that defence if you like—if you think it will be believed," retorted Foyle. "It will be better for every one if you tell the truth, though."

The man lapsed into a surly, sullen silence, and the superintendent could feel that he was glaring at him in the darkness of the closed car. The other detective looked through the window.

"Here comes Mr. Green, sir."

Arm in arm and in amicable converse with Ike, the chief detective-inspector was approaching the car, with the chauffeur on the other side. Ike, it appeared, had been run to earth in the dining-room, and had surrendered at discretion. He had all the philosophy of the habitual thief who knows when the game is up. He grinned a little when he saw the handcuffed policeman in the car.

"Why, it's you, Mr. Smith! Didn't you think I could be trusted for fair does over the stuff inside? You've fallen into it this time, and no blooming error. Where's Fred?"

"Fred who?" queried Foyle. "Is there some one else in this job?"

But Red Ike was too old a bird to be deceived. Instinct, as well as reason, told him that he had been betrayed, and the absence of Fred but lent fuel to his suspicions.

"Aw—don't come it, Mr. Foyle," he said disgustedly, and added a picturesque flow of language, elaborating the steps he would take to get even with Dutch Fred when he had the opportunity. Not one of the detectives interrupted him. The more he talked the better, for he might drop something of value. Not until they drew up at the police station did his eloquence desert him. The superintendent descended first and gave a few instructions, while the soi-disant constable was taken to the cells. Ike found himself escorted upstairs into the C.I.D. office. Only Heldon Foyle and Green remained with him.

"Sit down and make yourself comfortable," said the superintendent cheerfully. "We want to have a little talk with you, Ike. Would you like a drink? Here, have a cigar."

Red Ike's swift wits were on the alert. Never before had he known this kind of hospitality to be tendered in a police station to a man arrested red-handed. And although suspicious, he was nevertheless flattered. All criminals, whether at the top or bottom of their profession, are beset by vanity.

"A little out of your usual line this," went on Foyle, watching his man intently. "As neat a job as ever was spoiled by accident. Now you know, as well as I do, that we can't force you to talk. But it'll help us a bit if you tell us who you got those keys from, for instance."

The office was small and plainly furnished, and Ike stared into the fire as he sipped his whisky, with placid face. That the interview was to be the English equivalent of the third degree, he knew not. There would be no bullying, only coaxing. Foyle was in a position where consummate tact was needed if he was to extract anything from the prisoner. He dared neither threaten nor promise. However helpful Ike might be, he would still have to submit the issue of guilt and punishment to a judge and jury. Ike, unlike Dutch Fred, had no relations, and if he had it was doubtful if any promise of consideration for them would move him.

"It's no good, Mr. Foyle," said Ike. "The only man that was in this with me was Dutch Fred. You'd better go and get him, because I shall tell all about it in court. He gave me the keys."

"Don't be a fool, Ike," interposed Green.

The prisoner glanced from one to the other with cunning, twinkling eyes. He was too wary to say anything that may be used as evidence.

"I guess that it isn't bursting into the place that's put you two to work," he said. "You want to know something. If I could help you I s'pose you'd drop this case?"

Heldon Foyle shook his head resolutely.

"You know we can't do that in a case of felony. Mr. Green will put in a good word for you at the trial. That's the farthest we can go to."

Ike put down his empty glass. He believed he held the whip hand—that he had much to gain and nothing to lose by holding out for better terms. It was a false impression, though a natural one. Heldon Foyle had neither the power nor the inclination to drive a bargain that would permit Ike to go unscathed to renew his depredations on society.

"It's no good, guv'nor," said Ike. "If you want me to talk I'll do it—if you'll let me go."

"Right." Foyle rose abruptly. "We'll let it go at that, Ike. You please yourself, of course. Mr. Green, you'd better charge him now."

He had passed out of the door, and his footsteps were dying away when Ike awoke to the fact that his attempt at bluff had failed. He raised his voice. "Hi! Mr. Foyle! Don't go yet. I'll cough up what I know. Come back."