There was a deep silence. Tarling could feel his heart thumping almost noisily.

"After I had left Lyne's Store," she said, "I had decided to go to mother to spend two or three days with her before I began looking for work. Mr. Milburgh only went to Hertford for the weekends, and I couldn't stay in the same house with him, knowing all that I knew.

"I left my flat at about half-past six that evening, but I am not quite sure of the exact time. It must have been somewhere near then, because I was going to catch the seven o'clock train to Hertford. I arrived at the station and had taken my ticket, and was stooping to pick up my bag, when I felt a hand on my arm, and turning, saw Mr. Milburgh. He was in a state of great agitation and distress, and asked me to take a later train and accompany him to the Florentine Restaurant, where he had taken a private room. He told me he had very bad news and that I must know.

"I put my bag in the cloak-room and went off with him, and over the dinner—I only had a cup of tea, as a matter of fact—he told me that he was on the verge of ruin. He said that Mr. Lyne had sent for a detective (which was you), and had the intention of exposing him, only Mr. Lyne's rage against me was so great, that for the moment he was diverted from his purpose.

"'Only you can save me,' said Milburgh.

"'I?' I said in astonishment, 'how can I save you?'

"'Take the responsibility for the theft upon yourself,' he said. 'Your mother is involved in this heavily.'

"'Does she know?'

"He nodded. I found afterwards that he was lying to me and was preying upon my love for mother.

"I was dazed and horrified," said the girl, "at the thought that poor dear mother might be involved in this horrible scandal, and when he suggested that I should write a confession at his dictation and should leave by the first train for the Continent until the matter blew over, I fell in with his scheme without protest—and that is all."

"Why did you come to Hertford to-night?" asked Tarling.

Again she smiled.

"To get the confession," she said simply "I knew Milburgh would keep it in the safe. I saw him when I left the hotel—he had telephoned to me and made the appointment at the shop where I slipped the detectives, and it was there that he told me——" she stopped suddenly and went red.

"He told you I was fond of you," said Tarling quietly, and she nodded.

"He threatened to take advantage of that fact, and wanted to show you the confession."

"I see," said Tarling, and heaved a deep sigh of relief. "Thank God!" he said fervently.

"For what?" she asked, looking at him in astonishment.

"That everything is clear. To-morrow I will arrest the murderer of Thornton Lyne!"

"No, no, not that," she said, and laid her hand on his shoulder, her distressed face looking into his, "surely not that. Mr. Milburgh could not have done it, he could not be so great a scoundrel."

"Who sent the wire to your mother saying you were not coming down?"

"Milburgh," replied the girl.

"Did he send two wires, do you remember?" said Tarling.

She hesitated.

"Yes, he did," she said, "I don't know who the other was to."

"It was the same writing anyway," he said.

"But——"

"Dear," he said, "you must not worry any more about it. There is a trying time ahead of you, but you must be brave, both for your own sake and for your mother's, and for mine," he added.

Despite her unhappiness she smiled faintly.

"You take something for granted, don't you?" she asked.

"Am I doing that?" he said in surprise.

"You mean—" she went redder than ever—"that I care enough for you—that I would make an effort for your sake?"

"I suppose I do," said Tarling slowly, "it's vanity, I suppose?"

"Perhaps it is instinct," she said, and squeezed his arm.

"I must take you back to your mother's place," he said.

The walk from the house to the station had been a long and tedious one. The way back was surprisingly short, even though they walked at snail's pace. There never was a courting such as Tarling's, and it seemed unreal as a dream. The girl had a key of the outer gate and they passed through together.

"Does your mother know that you are in Hertford?" asked Tarling suddenly.

"Yes," replied the girl. "I saw her before I came after you."

"Does she know——"

He did not care to finish the sentence.

"No," said the girl, "she does not know. Poor woman, it will break her heart. She is—very fond of Milburgh. Sometimes he is most kind to mother. She loves him so much that she accepted his mysterious comings and goings and all the explanations which he offered, without suspicion."

They had reached the place where he had picked up the wallet, and above him gloomed the dark bulk of the portico with its glass-house atop. The house was in darkness, no lights shone anywhere.

"I will take you in through the door under the portico. It is the way Mr. Milburgh always comes. Have you a light?"

He had his electric lamp in his pocket and he put a beam upon the key-hole. She inserted the key and uttered a note of exclamation, for the door yielded under her pressure and opened.

"It is unlocked," she said. "I am sure I fastened it."

Tarling put his lamp upon the lock and made a little grimace. The catch had been wedged back into the lock so that it could not spring out again.

"How long were you in the house?" he asked quickly.

"Only a few minutes," said the girl. "I went in just to tell mother, and I came out immediately."

"Did you close the door behind you when you went in?"

The girl thought a moment.

"Perhaps I didn't," she said. "No, of course not—I didn't come back this way; mother let me out by the front door."

Tarling put his light into the hall and saw the carpeted stairs half-a-dozen feet away. He guessed what had happened. Somebody had seen the door ajar, and guessing from the fact that she had left it open that she was returning immediately, had slipped a piece of wood, which looked to be and was in fact the stalk of a match, between the catch of the spring lock and its sheath.

"What has happened?" asked the girl in a troubled voice.

"Nothing," said Tarling airily. "It was probably your disreputable step-father did this. He may have lost his key."

"He could have gone in the front door," said the girl uneasily.

"Well, I'll go first," said Tarling with a cheerfulness which he was far from feeling.

He went upstairs, his lamp in one hand, an automatic pistol in the other. The stairs ended in a balustraded landing from which two doors opened.

"That is mother's room," said the girl, pointing to the nearest.

A sense of impending trouble made her shiver. Tarling put his arms about her encouragingly. He walked to the door of the room, turned the handle and opened it. There was something behind the door which held it close, and exerting all his strength he pushed the door open sufficiently far to allow of his squeezing through.

On the desk a table-lamp was burning, the light of which was hidden from the outside by the heavily-curtained windows, but it was neither at the window nor at the desk that he was looking.

Mrs. Rider lay behind the door, a little smile on her face, the haft of a dagger standing out with hideous distinctness beneath her heart.