Waterloo Station, and you have no personal acquaintance with Mrs. Lester, what evidence can you give that will assist the police?"

"Mrs. Lester received a visitor last night, an incident so unusual that I, who heard him arrive, and Bates, who was in my sitting room when we both heard him depart, commented on the strangeness of it. That, I suppose, is the reason why I am in request by Scotland Yard."

"You say 'him.' How did you know it was a man? Did you see him?"

"Er-- that was impossible. We were in my flat, behind its closed door. Bates and I deduced his sex from the sound of his footsteps."

Again Theydon nearly stammered. Events had certainly turned in the most amazing way. Instead of carrying himself almost in the manner of a judge, he was figuring rather as an unwilling witness in the hands of a skilled and merciless cross-examining counsel.

"Did the police officers supply any theory of motive for the crime? Was this poor woman killed for the sake of her few trinkets?"

By this time Theydon was stung into a species of revolt. It was he, not Forbes, who should be snapping out searching questions.

"I regret to say that my nerves were not sufficiently under control at Waterloo that I should listen carefully to each word," he said, almost stiffly. "Bates had picked up such information as was available; but he, though an ex-sergeant in the Army, was so upset as to be hardly coherent. When I meet the detectives in the course of another hour I shall probably gather something definite and reliable in the way of details."

Forbes laid the pipe which he had filled but not lighted on the table. He poured out a glass of port and drank it.

"Try that," he said, pushing the decanter toward Theydon. "They cannot trouble you greatly. You have so little to tell."

"No, thanks. Nothing more for me tonight until the Scotland Yard men have cleared out."

Forbes rose as he spoke and strode the length of the room and back with the air of a man debating some weighty and difficult point.

"Mr. Theydon," he said, at last, halting in front of the younger man and gazing down at him with a direct intensity that was highly embarrassing to one who had good cause to connect him with the actual crime. "I want you to do me a favor-- a great favor. It was in my mind at first to ask you to permit me to go with you to Innesmore Mansions, and to be present during the interview with the detectives. But a man in my position must be circumspect. It would, perhaps, be unwise to appear too openly interested. I don't mind telling you in confidence that I have known Mrs. Lester many years. The shock of her death, severe as it must have been to you, is slight as compared with my own sorrow and dismay. More than that I dare not say until better informed. I remember now hearing the newsboys shouting their ghoulish news, and I saw contents bills making large type display of 'Murder of a lady,' but little did I imagine that the victim was one whom-- one whose loss I shall deplore.... Are you on the telephone?"

"Yes," said Theydon, thoroughly mystified anew by the announcement that Forbes had even contemplated, or so much as hinted at, the astounding imprudence of visiting Innesmore Mansions that night.

"Ring me up when the detectives have gone. I shall esteem your assistance during this crisis as a real service."

For the life of him, Theydon could not frame the protest which ought to have been made without delay and without hesitation.

"Yes," he said. "I'll do that. You can trust me absolutely."

Thus was he committed to secrecy. That promise sealed his lips.

CHAPTER III

IN THE TOILS

Theydon, though blessed, or cursed, with an active imagination-- which must surely be the prime equipment of a novelist-- was shrewd and level-headed in dealing with everyday affairs.

It was no small achievement that the son of a country rector, aided only by a stout heart, a university education and an excellent physique-- good recommendations, each and all, but forming the stock-in-trade of many a man on whose subsequent career "failure" is writ large-- should have forced himself to the front rank of the most overcrowded among the professions before attaining his twenty-sixth year.

It may be taken for granted, therefore, that he was not lacking in the qualities of close observation and critical analysis. He would, for instance, be readier than the majority of his fellows to note the small beginnings of events destined to become important.

Often, of course, his deductions would prove erroneous, but the mere fact that he habitually exercised his wits in such a way rendered it equally certain that his judgment would be accurate sometimes. One such occasion presented itself a few seconds after he had left the Forbes mansion.

A taxi, summoned by a footman, was in waiting, and Theydon was crossing the pavement when he noticed a gray landaulet car at rest beneath the trees at some distance. Mr. Forbes's house stood in a square, and the gray car had been drawn up on the quiet side of the roadway, being stationed there, apparently, to await its owner's behest. Gray cars are common enough in London, but they are usually of the touring class.

Not often does one see a gray-painted landaulet; hence, the odd though hardly remarkable fact occurred to Theydon that a precisely similar gray automobile had occupied the center of the station yard at Waterloo when he took a taxi from the rank.

Admittedly he was in a nervous and excited state. It could hardly be otherwise after the strain of that astounding conversation with Forbes, and there was no prospect of the tension being relaxed until the close of the interview with the detectives, which he now regarded as the worse ordeal of the two.

But this subconscious neurasthenia in no wise affected the reflex action of his ordinary faculties. When, on leaving the square, and while his cab was rattling along an aristocratic thoroughfare leading to Knightsbridge, he peered through a tiny observation window in the back of the vehicle, and ascertained that the gray car was stealing along quietly about a hundred yards in the rear, he began to believe that its presence both at Waterloo and outside Mr. Forbes's residence could not be wholly accidental. When he had watched its persistent treading on his heels along Piccadilly its intent became almost unmistakable.

The route to Innesmore Mansions traversed some of London's main arteries, but, despite the rush of traffic due to the first flight of homewardbound playgoers, the gray car kept steadily on his track. Amused at first, be became angry because of a notion which grew out of the wonderment of finding himself the object of this persistent espionage.

To make sure, and at the same time discover the sort of person who was spying on him, he adopted a ruse. Leaning out, when about to cross Oxford Street into Tottenham Court Road, he said to his driver: "Turn sharp to the right in Store Street, and pull up. I'll tell you when to go on again."

The man obeyed. Theydon posted himself at the outer window, and in a space of time so short that the excellence of the gray car's accelerator was amply demonstrated, the pursuer swung into sight. A stolid-faced chauffeur at the wheel did not appear discomfited at coming on his quarry thus unexpectedly. He whirled past, seemingly quite oblivious of Theydon's fixed stare. Though the weather was mild he wore an overcoat with upturned collar, so that between its protecting flaps and a low-peaked cap his face was well hidden. Still, Theydon received an impression of a curiously wooden physiognomy.

The man might have been an automaton for all the heed he gave to the taxi or its inquisitive occupant. But his aspect was almost forgotten in the far stranger discovery that the car was empty. Both windows were open, and the bright lights of a corner shop flashed into the interior, yet not a soul was visible. Moreover, the car sped on unhesitatingly, stopping some two hundred yards ahead.

So far as Theydon could tell, no one alighted. He jotted down the number-- XY 1314-- on his shirt cuff.

"Did you happen to see that car waiting near the house I came from?" he said to the taxi man, who, of course, provided an interested audience of one.

"Yes, sir," was the ready answer. "It's not a London car. I've never seen them letters afore."

"In other words, it may be a faked number."

"Likely enough, sir, but rather risky. The police are quick at spotting that sort of thing."

"Can you take a hand in the game? I want to know where that car goes to."

The man grinned.

"I wouldn't like to humbug you, sir. That there machine can lose me quicker'n a Derby winner could pass a keb horse. Didn't you hear the hum of the engine as it went by?"

"Thanks. Now go ahead to Innesmore Mansions."

He was paying the driver when the gray car stole quietly past the end of the street, and that was the last he saw of it.

"There it goes again, sir," said the man. "Tell you wot, gimme your name an' address. I'll make a few inquiries, an' keep me eyes open as well. Then, if I hear anythink, I'll let you know."

Theydon scribbled the number of his flat on a card.

"There you are," he said. "Even if I happen to be out, I'll leave instructions that you are to be paid half a crown for your trouble if you call. By the way, what is your name?"