"I don't understand," he stammered. "He-Nepcote-why should he be watching us?"

"Because he penetrated the truth last night. He knew he was in danger."

"But why should he follow us here?"

"He accidentally dropped some cards from his pocket-book when giving Merrington an address at his flat last night, and one of them was Wendover's business card. Merrington did not see it-it would have conveyed nothing to him if he had-but I did. Nepcote knew that I saw it, and must have realized that I suspected him. He has been watching my rooms and followed us here, or he has been hanging around this place to see if I called on Wendover."

"Even now I do not see the connection. If Wendover told us the truth, Nepcote has not been to him with the necklace. Then what did it matter to Nepcote whether you came here or not?"

"Nepcote may have been the man who offered the diamond to Wendover."

"That is impossible. Wendover says that man called some days before the murder."

"Still, it may have been Nepcote."

"That goes beyond me," said Caldew, with a puzzled look. "What are you implying?"

"Nothing at present. Every step in this case convinces me that we are faced with a very deep mystery. It isn't worth while to hazard a guess, because guessing is always unsatisfactory."

"Perhaps we had better try and get a little more out of Wendover," said Caldew.

"That would be merely waste of time. He has not got the necklace, and he is unable to describe the man who offered him the diamond. I believe now that it was Nepcote, but that doesn't matter, one way or another. It is far more important to know that he came here to-day to watch for us. That implies that he had reason to fear investigations about the necklace. The inference to be drawn is that Nepcote is responsible for the disappearance of the necklace, and is, therefore, deeply implicated in the murder."

"Perhaps it was not Nepcote that you saw?" suggested Caldew. He felt that the remark was a feeble one, but he was bewildered by the sudden turn of events, and in a frame of mind which clutches at straws.

"Put that doubt out of your mind," said Colwyn. "I saw his face distinctly. He had disappeared by the time I got down. The alley where he was standing commanded a view of the entrance of this building. I ascertained that by standing in the same spot. His flight is another proof-though that was not needed-of his guilty knowledge and complicity in this murder. Why should he run away? According to his own story last night he had nothing to fear. But now, by his own actions, he has brought the utmost suspicion on himself."

"I suppose it is no use searching about here for him?" remarked Caldew, glancing gloomily out of the doorway.

"Not in the least. The neighbourhood is a warren of alleys and side streets from here to Grays Inn Road."

"Then I shall go up to his flat at once," said Caldew. "He has not had time to go back."

"He will not return to his flat. We have seen the last of him until we catch him. He has had two warnings, and he is not likely to be guilty of the folly of waiting to see whether lightning strikes thrice in the same spot. He will get away for good, this time, if he can. Nevertheless it is worth while going to the flat. We may pick up some points there." Colwyn uttered these last words in a lower tone at the sight of two office girls descending the staircase with much chatter and laughter.

"Let us go then."

They travelled by 'bus from Grays Inn Road as far as Oxford Circus, and walked along a number of quiet secluded streets-the backwaters of the West End-in order to reach Sherryman Street from the lower end, which, with a true sense of the fitness of things, was called Sherryman Street Approach. If the Approach had not been within a stone's throw of Sherryman Square it might have been called a slum. It had tenement houses with swarms of squalid children playing in the open doorways, its shops offered East End food-mussels and whelks, "two-eyed steaks," reeking fish-and-chips, and horsemeat for the cheap foreign element. There were several public-houses with groups of women outside drinking and gossiping, all wearing the black shawls which are as emblematic of the lower cla.s.s London woman as a chasuble to a priest, or a blue tattooed upper lip to a high-caste Maori beauty. A costermonger hawked frozen rabbits from a donkey-cart, with a pallid woman following behind to drive away the mangy cats which quarrelled in the road for the oozing blood which dripped from the cart's tail. An Italian woman, swarthy, squat, and intolerably dirty, ground out the "Ma.r.s.eillaise" from a barrel-organ with a shivering monkey capering atop, waving a small Union Jack, and impatiently rattling a tin can for coppers.

To turn from this squalid quarter into Sherryman Street was to pa.s.s from the east to the west end of London at a step. It was as though an invisible line of demarcation had been drawn between the lower and upper portion of the street, and held inviolate by the residents of each portion. There were no public houses or fish-shops in Sherryman Street; no organ-grinders, costermongers, unclean children, or women in black shawls. It had quiet, seclusion, clean pavements, polished doorknockers, and white curtains at the windows of its well-kept houses, which grew in dignity to the semblance of town mansions at the Square end.

Number 10 showed a blank closed stone exterior to the pa.s.ser-by, like an old grey secretive face. As they approached it Colwyn, with a slight movement of his head, drew his companion's attention to the upper windows which belonged to Nepcote's flat. The blinds were down.

"It looks as if Nepcote left last night," he said.

The sight of the drawn blinds, like yellow eyelids in the grey face, awakened some secret irritation in Caldew's breast, and with it the realization of his powers as an officer of Scotland Yard.

"I shall force a way in and see," he angrily declared.

"Better get a key from the housekeeper," suggested Colwyn. "The women who look after these bachelor flats always have duplicate keys. But the front door is ajar. Let us go upstairs first."

They ascended the stairs to the flat, and the first thing they noticed was a Yale key in the keyhole of the door.

"A sign of mental upset," commented Colwyn. "At such moments people forget the little things."

They opened the door and entered. The front room was much as Colwyn had seen it the previous night. The flowers drooped in their bowl; the chorus girls smirked in their silver settings; the framed racehorses and their stolid trainers looked woodenly down from the pink walls.

"Nepcote does not seem to have taken anything away with him," remarked Caldew, looking into the bedroom. "The wardrobe is full of his uniforms, but the bed has not been occupied."

"Here is the proof that he has fled," said Colwyn, flinging back the lid of a desk which stood in the sitting-room. It was filled to the brim with a ma.s.s of torn papers.

"Anything compromising?" asked Caldew, eagerly approaching to look at the litter.

"No; only bills and invitations. Any dangerous letters have been burnt there." He pointed to the grate, which was heaped with blackened fragments. "He's made a good job of it too," he added, as he went to the fireplace and bent over it. "There's not the slightest chance of deciphering a line. But it would be as well to search his clothes. He may have forgotten some letters in the pockets."

Caldew took the hint, and disappeared into the inner room, leaving Colwyn examining the contents of the grate. He returned in a few minutes to say that he had found nothing in the clothes except a few Treasury notes and some loose silver in a trousers' pocket.

"That looks as if he had bolted in such a hurry that he forgot to take his change with him," said Colwyn. "It is another interesting revelation of his state of mind, because there is very little doubt that he returned to the flat this morning after leaving it last night."

"How do you arrive at that conclusion?"

"By the burnt letters in the grate. They are still warm. He was in such a state of fear that he dared not sleep in the flat last night, but he returned this morning to burn his letters and change into civilian clothes. Then he rushed away again in such a hurry that he forgot his money. There is nothing more to be seen here. We had better make a few inquiries of the housekeeper as we go downstairs."

They walked out, and Caldew locked the door behind him and placed the key in his pocket. When they reached the entrance hall Colwyn paused outside the door of the recess where the housekeeper lurked, like an octopus in a pool. At Colwyn's knock a white face, topped by a white cap, came into view through the narrow slit in the curtained gla.s.s half of the door, and swam towards them in the interior gloom after the manner of the head of a materialized ghost in a spirit medium's parlour. The door opened, and the apparition appeared in the flesh, looking at them with stony eyes. Caldew undertook the conversation:

"Did Captain Nepcote sleep here last night?" he curtly asked.

"I don't know."

"Well, has he been here this morning?"

"I don't know." The tone of the second reply was even more expressionless than the first, if that were possible.

"It's your business to know," said Caldew angrily.

"It is not my business to discuss Captain Nepcote's private affairs with strangers." The woman turned back into her room without another word, closing the door behind her.

"D-n her!" muttered Caldew, in intense exasperation.

"These ancient females learn the wisdom of controlling their natural garrulity when placed in charge of bachelors' flats," said Colwyn with a laugh. "We will get nothing out of her if we stay here all day, so we had better go."

"I am going straight back to Scotland Yard," Caldew announced with sudden decision when they reached the pavement. "I must tell Merrington all about this morning's work, and the sooner the better. We must have the flat watched. Perhaps Nepcote may return."

"He will not return," said Colwyn. "He knows that we are after him, and that the flat will be watched. But it is a good idea not to let him have too long a start. Come, let us see if we can find a taxi, and I will drop you at Scotland Yard."

They walked along to Sherryman Square, and esteemed themselves fortunate in picking up a cruising taxi-cab with a driver sufficiently complaisant to drive them in the direction they wished to go.

CHAPTER XXII