Five minutes after Big Ben had struck ten o'clock Heldon Foyle walked into his office to find Sir Ralph Fairfield striding up and down and glancing impatiently at the clock. He made no direct answer to the detective's salutation, but plunged at once into the object of his visit.

"Have you seen the Wire this morning?" he asked abruptly.

Foyle seated himself at his desk, imperturbable and unmoved.

"No," he answered, "but I know of the advertisement that brought you here. As a matter of fact, I sent it to the paper. I should have called on you if you hadn't come. Grell meant it for you, right enough."

The significance of the detective's admission that he knew of the advertisement did not immediately strike Fairfield. He unfolded a copy of the Daily Wire.

"What do you make of the infernal thing?" he demanded. "It's absolute Greek to me."

With a letter selected from the pile of correspondence on his desk unopened in his hand, Heldon Foyle swung round and faced his questioner.

"It's simply a sighting shot, Sir Ralph," he remarked quietly. "Grell credits you with intelligence enough to remember that number later. Have you any knowledge of ciphers?"

"I have an elementary idea that to unravel them you work from the most frequently recurring letter; E, isn't it?"

"That's right," said Foyle. "But there are other ciphers where that system won't work. Mind you, I don't pose as an expert. If I had a cipher to unravel, I should go to a man who had specialised in them, exactly as I should go to a doctor on a medical question. Still, the advertisement to-day isn't a cipher. It means exactly what it says."

"Thank you," said Fairfield drily. "I am now as wise as when I started."

"Sorry," murmured Foyle suavely. "You'll be wiser presently. The thing isn't complete yet. If you'll excuse me a few minutes, I'll just run through my letters, and then, if you don't mind taking a little walk, we'll go and see Lady Eileen Meredith."

Some formal reply rose to Fairfield's lips—he never knew what. The last time he had seen Eileen was fixed in his memory. Then she had practically denounced him as a murderer. Since then she had learnt that every shadow of suspicion had been cleared away from him. How would she receive him if he visited her unexpectedly with Foyle? Why did Foyle wish him to go? Perhaps, after all, there was nothing in it. He told himself fiercely that there was no reason why the meeting should embarrass him. Some day, sooner or later, they would have to meet. Why not now? He was hungry for a sight of her, and yet he was as nervous as a child at the thought of going to her.

The slamming of a drawer and the soft click of a key in the lock told that Foyle had finished. He picked up a copy of the Daily Wire and his hat and gloves.

"Now, Sir Ralph," he said briskly, and together they descended the narrow flight of stone steps which leads to one of Scotland Yard's back doors. The detective was apparently in a talkative mood, and Fairfield got no chance to ask the questions that were filling his mind. Spite of himself he became interested in the flow of anecdotes which came from his companion's lips. There were few corners of the world, civilised or uncivilised, where the superintendent had not been in the course of his career. He had the gift of dramatic and humorous story-telling. He spoke of adventures in Buenos Ayres, in South Africa, Russia, the United States, and a dozen other countries, of knife-thrusts and revolver shots, of sand-bagging and bludgeoning, without any suspicion of vaunting himself. The baronet made some comment.

"No," said Foyle. "Take it all round, a detective's life is more monotonous than exciting. It's taken me thirty years to collect the experiences I'm telling you about. Things always happen unexpectedly. Some of my narrowest squeaks have taken place in England, in the West End. Why, I was nearly shot in one of the best hotels by an officer sent over from the United States to take charge of a man I had arrested. He was the sheriff of some small town and had a bit of a reputation as a gun-man, and had come over with the district attorney to escort the chap back. They did themselves well while they were here waiting to catch a boat back. One morning I strolled into the hotel, and who should run into me but the attorney with a face the colour of white paper.

"'That you, chief?' he gasps. 'For God's sake don't go upstairs. ——'s on the landing, blazing drunk and with his gun out. He's a dead shot.'

"Well, I could see that a Wild West sheriff was out of place in a decent hotel, so up I went. He had me covered like a flash, and I yelled out to him not to shoot.

"'Hello, chief,' he says. 'That's all right. Come right up. I won't do a thing. Just wait till I've plugged that cur of an attorney and we'll go and have a drink.'

"By this time I was up level with him. I daren't risk trying to get the revolver from him, for he was a quick shot, so I pushed my arm through his.

"'I haven't got much time, sheriff,' says I. 'Let's go and have a drink first, and you settle up with him afterwards.'

"'That's a bet,' he says, and I led him down to the bar. I persuaded him to try a new drink of my own invention—its chief component was soda-water—and followed it up with strong hot coffee. Meanwhile I managed to get the gun away, on the pretext of admiring it. He was reluctant at first, telling me I could have it for keeps after he had finished that cur of an attorney. But I got it, and he was fairly sober by the time I left him.

"Then there was a sequel. I had warned the sheriff and the attorney, who had made up their differences, that the man they had got was a slippery customer to handle. However, they got him in the boat all right. When they got to New York I had a cable from the captain—a friend of mine. He said the prisoner had not only cleared off the ship by himself, but had carried away the hand-baggage of his escort."

This reminiscence had brought them to Berkeley Square. Fairfield felt his heart thumping quickly although his face was impassive as the door was opened in response to Foyle's ring. She might be out; she might refuse to see them. Neither of the two alternatives happened. Within three minutes Eileen had descended to them in the drawing-room.

She stopped, a graceful figure in black, by the doorway, and gave a barely perceptible start as her eyes rested on the baronet. She bowed coldly.

"I did not know you were here, Sir Ralph. I understood Mr. Foyle wished to see me."

She was frigid and self-possessed. He had half expected some expression of apology for the wrong she had done him, but she entirely ignored that. But that Fairfield had himself well in hand he would have openly resented the snub inflicted on him. It was Foyle who answered.

"I brought Sir Ralph here. I thought his presence might be necessary."

She moved across the room, and sank on a couch with a petulant frown.

"Well, I suppose you have some disagreeable business to transact. Let us get it over."

The superintendent knew that he was dealing with a woman entirely on her guard. Her steady grey eyes were fixed on him closely, as though she could read his thoughts. He thought he could detect a slight twitching of the slender hands that rested idly on her lap.

"I want to know," he said slowly, "the meaning of the advertisement addressed to you by Robert Grell in this morning's Daily Wire."

He could have sworn that his shot had hit, that she flinched a little as he spoke. But if so she showed no further sign. Instead, her face was all astonishment as she replied—

"I don't quite understand. What advertisement? I know nothing about Mr. Grell since he left Grosvenor Gardens. Will you explain?"

Deliberately the superintendent took from his breast-pocket a copy of the Daily Wire, folded back at the personal column, and read:

"E. £27.14.5. To-morrow. B."

"That," he said, "is addressed to you. It is hardly worth while denying knowledge of it. It was found last night on a man arrested for attempted housebreaking at Mr. Grell's house. I ordered that it be sent to the paper, together with another intended for the eye of Sir Ralph Fairfield."

Her interest was plainly awakened.

"Then the other was for you!" she cried, turning to Fairfield. "I wondered if——"

She paused with the realisation that she had admitted what she had a moment before denied. Foyle's foot pressed heavily on the toe of the baronet to warn him not to speak.

"Yes, it was for Sir Ralph," he said. "That is why I brought him here. It is you, though, who hold the key to this mystery. We know that you would have sent your jewels to Grell, that you are in communication with his friends. You are young, Lady Eileen, and don't realise that you are playing with fire. Your silence can do your lover no good—it may do him and yourself harm. You have been visited by the Princess Petrovska, an adventuress not fit to touch the hem of your skirt. You are already involved. Take the advice of a man old enough to be your father, and confide in us."

She had risen, and her slim form towered over the seated detective. She seemed about to resent his words, but suddenly burst into a ripple of laughter.

"You would be offensive if you were not amusing, Mr. Foyle. Don't you think my help would be a little superfluous, since you know so much?" she asked with a quietness that robbed the remark of some of its bitterness. "I think you had better go now."

"I am sorry," said Foyle. "You may regret that you did not take my advice."

She herself held the door open for them to pass out. To the surprise of Fairfield, she held out her hand to him while ignoring the detective.

"Come back alone as soon as you can," she whispered. "I want to speak to you."

Foyle had apparently neither heeded nor heard. Yet, as soon as they were out of eye-shot of the house, he turned to Fairfield.

"She asked you to go back?"

"Eh?" The baronet was startled. "Yes. How did you know? Did you overhear her?"

"No, but I hoped she would when I took you there. That was the whole reason of our visit. I didn't expect to get her to say or admit anything."

Fairfield came to an abrupt halt and gripped his companion by the arm.

"You intended— For what reason? How could you know?"

"Absolute common sense, my dear sir. That's all. Absolute common sense. If you are a chess-player, you know that the man who can foretell what move his opponent is going to make usually wins. Here, let's find a quiet Piccadilly tea-shop and I'll tell you all about it."

There is no place which one may find more convenient for a quiet conversation than the London tea-shop before twelve in the morning. Over a cup of coffee in the deserted smoking-room Foyle spoke to the point.

"I did not tell you why I took you to see Lady Eileen, because I was afraid you might refuse. She has been antagonistic to you hitherto. The fact that Grell advertised you in somewhat the same manner as herself has given her the idea that, after all, you too might be trying to shield him. Naturally, she wants to be certain, in order that you may join forces. That's why I prevented you saying anything. Now, if you go back to her you may tell her that I practically forced you to accompany me. You can win her confidence, and through her we may get on the right track."

An angry flush mounted to Fairfield's temples.

"In short," he said curtly, "you want me to act as a spy on an unsuspecting girl. No, thanks. That's not in our bargain."

He was genuinely angry at the proposal. The superintendent saw that he had been too blunt, and made haste to repair his error.

"Don't be in a hurry," he protested. "The girl, as I told her, is beginning to be mixed up in a dangerous business. This is the only way to extricate her. You may help her and Grell and us by doing as I ask. Consider it coolly, and you will see it is the best thing to do."

Sir Ralph set down his cup and fingered his watch-chain. Foyle signalled the waitress, paid the bill, lit a cigar and waited.

"I'll have to think over it," said Fairfield thoughtfully. "Give me an hour or two."

"Right you are," agreed the detective heartily, and they made their way out into the street.