And how would he get into the house? Rolfe had himself locked up the house and had locked the gates, and the bunch of keys was at that moment hanging up in Inspector Chippenfield's room in Scotland Yard. But even as he asked that question, Rolfe found himself smiling at himself for his simplicity. Nothing could be easier for a man like Hill--an ex-criminal--to have obtained a duplicate key, before handing over possession of the keys. Rolfe had noticed with surprise when he was locking up the house that the French windows of the morning room were locked from the outside by a small key as well as being bolted from the inside. Hill had explained that the late Sir Horace Fewbanks had generally used this French window for gaining access to his room after a nocturnal excursion.

Rolfe looked at his watch. It was nine o'clock. He decided to go to Hampstead and put his suspicions to the test. It was quite possible he was mistaken, but if, on the other hand, Hill was paying a nocturnal visit to Riversbrook and he had the luck to capture him, he might extract from him some valuable evidence for the forthcoming trial that Hill had kept back. And Rolfe was above all things interested at that moment in making the case for the prosecution as strong as possible.

Rolfe walked to the Camden Town Underground station, bought a ticket for Hampstead, and took his seat in the tube in that state of exhilarated excitement which comes to the detective when he feels that he is on the road to a disclosure. The speed of the train seemed all too slow for the police officer, and he looked at his watch at least a dozen times during the short journey from Camden Town to Hampstead.

When Rolfe arrived at Hampstead he set out at a rapid walk for Riversbrook. It was quite dark when he reached Tanton Gardens. He turned into the rustling avenue of chestnut trees, and strode swiftly down till he reached the deserted house of the murdered man.

The gate was locked as he had left it, but Rolfe climbed over it. A late moon was already throwing a refulgent light through the evening mists, silvering the tops of the fir trees in front of the house. Rolfe walked through the plantation, his footsteps falling noiselessly on the pine needles which strewed the path. He quickly reached the other side of the little wood, and the Italian garden lay before him, stretching in silver glory to the dark old house beyond.

Rolfe stood still at the edge of the wood, and glanced across the moonlit garden to the house. It seemed dark, deserted and desolate. There was no sign of a light in any of the windows facing the plantation.

The moon, rising above the fringe of trees in the woodland which skirted the meadows of the east side of the house, cast a sudden ray athwart the upper portion of the house. But the windows of the retreating first story still remained in shadow. Rolfe scrutinised these windows closely. There were three of them--he knew that two of them opened out from the bedroom the dead man used to occupy, and the third one belonged to the library adjoining--the room where the murder had been committed. The moonlight, gradually stealing over the house, revealed the windows of the bedroom closed and the blinds down, but the library was still in shadow, for a large chestnut-tree which grew in front of the house was directly in the line of Rolfe's vision.

Rolfe remained watching the house for some time, but no sign or sound of life could he detect in its silent desolation. "I must have been mistaken," he muttered, with a final glance at the windows of the first story. "There's n.o.body in the house."

He turned to go, and had taken a few steps through the pinewood when suddenly he started and stood still. His quick ear had caught a faint sound--a kind of rattle--coming from the direction of the house. What was that noise which sounded so strangely familiar to his ears? He had it! It was the fall of a Venetian blind. Instantaneously there came to Rolfe the remembrance that Inspector Chippenfield had ordered the library blind to be left up, so that when the sun was high in the heavens its rays, striking in through the window over the top of the chestnut-tree, might dry up the stain of blood on the floor, which washing had failed to efface. Somebody was in the library and had dropped the blind.

Rolfe hurriedly retraced his steps to the edge of the plantation, and raced across the Italian garden, feeling for his revolver as he ran. Some instinct told him that he would find entrance through the French windows on the west side of the morning room, and thither he directed his steps.

He pulled out his electric torch and tried the windows. They were shut, and the first one was locked. The second one yielded to his hand. He pulled it open, and stepped into the room. Making his way by the light of his torch to the stairs, he swiftly but silently crept up them and turned to the library on the left of the first landing. The door was closed but not locked, and a faint light came through the keyhole. Rolfe pushed the door open, and looked into the room. A man was leaning over the dead judge's writing-desk, examining its contents by the light of a candle which he had set down on the desk. He was so engrossed in his occupation that he did not hear the door open.

"What are you doing there?" demanded Rolfe sternly. His voice sounded hollow and menacing as it reverberated through the room.

The man at the desk started up, and turned round. It was Hill. When he saw Rolfe he looked as though he would fall. He made as if to step forward. Then he stood quite still, looking at the officer with ashen face.

"Hill," said Rolfe quietly, "what does this mean?"

The butler had regained his self-composure with wonderful quickness. The mask of reticence dropped over his face again, and it was in the smooth deferential tones of a well-trained servant that he replied:

"Nothing, sir, I just slipped over from the shop to see if everything was all right."

"How did you get into the house?"

"By the French window, sir. I had a duplicate key which Sir Horace had made."

"And I see you also have a duplicate key of the desk. Why didn't you give these keys up with the others to Inspector Chippenfield?"

"I forgot about them at the time, sir. I found them in an old pocket this evening, and I was so uneasy about the house shut up with a lot of valuable things in it and n.o.body to give an eye to them that I just slipped across to see everything was all right."

"You came here after dark, and let yourself in with a private key after you had been strictly ordered not to come near the place? You have the audacity to admit you have done this?"

"Well, it's this way, sir. I was a trusted servant of Sir Horace's. I knew a great deal about his private life, if I may say so. I know he kept a lot of private papers in this room, and I wanted to make sure they were safe--I didn't like them being in this empty house, sir. I couldn't sleep in my bed of nights for thinking of them, sir. I felt last night as if my poor dead master was standing at my bedside, urging me to go over. I am very sorry I disobeyed the police orders, Mr. Rolfe, but I acted for the best."

"Hill, you are lying, you are keeping something back. Unless you immediately tell me the real reason of your visit to this house tonight I will take you down to the Hampstead Police Station and have you locked up. This visit of yours will take a lot of explaining away after your previous confession, Hill. It's enough to put you in the dock with Birchill."

Hill's eyes, which had been fixed on Rolfe's face, wavered towards the doorway, as though he were meditating a rush for freedom. But he merely remarked:

"I've told you the truth, sir, though perhaps not all of it. I came across to see if I could find some of Sir Horace's private papers which are missing."

"How do you know there are any papers missing?"

"As I said before, Mr. Rolfe, Sir Horace trusted me and he didn't take the trouble to hide things from me."

"You mean that he often left his desk open with important papers scattered about it?"

"Yes, sir."

"And you made a practice of going through them?"

"I didn't make a practice of it," protested Hill. "But sometimes I glanced at one or two of them. I thought there was no harm in it, knowing that Sir Horace trusted me."

"And some papers that you knew were there are now missing. Do you mean stolen?"

"Yes, sir."

"When did you see them last?"

"Just before Inspector Chippenfield came--the morning after the body was discovered. You remember, sir, that he came straight up here while you stayed downstairs talking to Constable Flack."

"Do you mean to suggest that Inspector Chippenfield stole them?"

"Oh, no, sir, I don't think he saw them. Sir Horace kept them in this little place at the back of the desk. Look at it, sir. It's a sort of secret drawer."

Rolfe went over to the desk, and Hill explained to him how the hiding place could be closed and opened. It was at the back of the desk under the pigeonholes, and the fact that the pigeonholes came close down to the desk hid the secret drawer and the spring which controlled it.

"What was the nature of these papers?" asked Rolfe.

"Well, sir, I never read them. Sir Horace set such store by them that I never dared to open them for fear he would find out. They were mostly letters and they were tied up with a piece of silk ribbon."

"A lady's letters, of course," said Rolfe.

"Judging from the writing on the envelopes they were sent by a lady,"

said Hill.

Rolfe breathed quickly, for he felt that he was on the verge of a discovery. Here was evidence of a lady in the case, which might lead to a startling development. Perhaps Crewe was right in declaring that Birchill was the wrong man, he said to himself. Perhaps the murderer was not a man, but a woman.

"And who do you think stole them?" he asked Hill.

"That is more than I would like to say," replied the butler.

"Are you sure they were in this hiding place when Inspector Chippenfield took charge of everything?"

"Yes, sir. I dusted out the room the morning you and he came to Riversbrook together, and the papers were there then, because I happened to touch the spring as I was dusting the desk, and it flew open and I saw the bundle there."

"Why didn't you tell Inspector Chippenfield about the papers and the secret drawer?"

"That is what I intended to do, sir, if he didn't find them himself. But when I had found they had gone I didn't like to say anything to him, because, as you may say, I had no right to know anything about them."

"When did they go: when did you find they were missing?"