"But don't you realise that you may be charged with being an accessory before or after the act?" he urged. "Don't you see what it means to you and to your mother?"

Her eyes closed at the mention of her mother's name, as though to shut out the vision of some unpleasant possibility.

"Don't talk about it, don't talk about it!" she murmured, "please, Mr. Tarling! Do as you wish. Let the police arrest me or try me or hang me-but do not ask me to say any more, because I will not, I will not!"

Tarling sank back amongst the cushions, baffled and bewildered, and no more was said.

Whiteside was waiting for the train, and with him were two men who were unmistakably branded "Scotland Yard." Tarling drew him aside and explained the situation in a few words.

"Under the circumstances," he said, "I shall not execute the warrant."

Whiteside agreed.

"It is quite impossible that she could have committed the murder," he said. "I suppose the doctor's evidence is unshakable?"

"Absolutely," said Tarling, "and it is confirmed by the station master at Ashford, who has the time of the accident logged in his diary, and himself assisted to lift the girl from the train."

"Why did she call herself Miss Stevens?" asked Whiteside. "And what induced her to leave London so hurriedly?"

Tarling gave a despairing gesture.

"That is one of the things I should like to know," he said, "and the very matter upon which Miss Rider refuses to enlighten me. I am taking her to an hotel," he went on. "To-morrow I will bring her down to the Yard. But I doubt if the Chief can say anything that will induce her to talk."

"Was she surprised when you told her of the murder? Did she mention anybody's name?" asked Whiteside.

Tarling hesitated, and then, for one of the few times in his life, he lied.

"No," he said, "she was just upset ... she mentioned nobody."

He took the girl by taxi to the quiet little hotel he had chosen-a journey not without its thrills, for the fog was now thick-and saw her comfortably fixed.

"I can't be sufficiently grateful to you, Mr. Tarling, for your kindness," she said at parting "and if I could make your task any easier ... I would."

He saw a spasm of pain pass across her face.

"I don't understand it yet; it seems like a bad dream," she said half to herself. "I don't want to understand it somehow ... I want to forget, I want to forget!"

"What do you want to forget?" asked Tarling.

She shook her head.

"Don't ask me," she said. "Please, please, don't ask me!"

He walked down the big stairway, a greatly worried man. He had left the taxi at the door. To his surprise he found the cab had gone, and turned to the porter.

"What happened to my taxi?" he said. "I didn't pay him off."

"Your taxi, sir?" said the head porter. "I didn't see it go. I'll ask one of the boys."

As assistant porter who had been in the street told a surprising tale. A gentleman had come up out of the murk, had paid off the taxi, which had disappeared. The witness to this proceeding had not seen the gentleman's face. All he knew was that this mysterious benefactor had walked away in an opposite direction to that in which the cab had gone, and had vanished into the night.

Tarling frowned.

"That's curious," he said. "Get me another taxi."

"I'm afraid you'll find that difficult, sir." The hotel porter shook his head. "You see how the fog is-we always get them thick about here-it's rather late in the year for fogs..."

Tarling cut short his lecture on meteorology, buttoned up his coat, and turned out of the hotel in the direction of the nearest underground station.

The hotel to which he had taken the girl was situated in a quiet residential street, and at this hour of the night the street was deserted, and the fog added something to its normal loneliness.

Tarling was not particularly well acquainted with London, but he had a rough idea of direction. The fog was thick, but he could see the blurred nimbus of a street lamp, and was midway between two of these when he heard a soft step behind him.

It was the faintest shuffle of sound, and he turned quickly. Instinctively he threw up his hands and stepped aside.

Something whizzed past his head and struck the pavement with a thud.

"Sandbag," he noted mentally, and leapt at his assailant.

As quickly his unknown attacker jumped back. There was a deafening report. His feet were scorched with burning cordite, and momentarily he released his grip of his enemy's throat, which he had seized.

He sensed rather than saw the pistol raised again, and made one of those lightning falls which he had learnt in far-off days from Japanese instructors of ju-jitsu. Head over heels he went as the pistol exploded for the second time. It was a clever trick, designed to bring the full force of his foot against his opponent's knee. But the mysterious stranger was too quick for him, and when Tailing leapt to his feet he was alone.

But he had seen the face-big and white and vengeful. It was glimpse and guess-work, but he was satisfied that he knew his man.

He ran in the direction he thought the would-be assassin must have taken, but the fog was patchy and he misjudged. He heard the sound of hurrying footsteps and ran towards them, only to find that it was a policeman attracted by the sound of shots.

The officer had met nobody.

"He must have gone the other way," said Tarling, and raced off in pursuit, without, however, coming up with his attacker.

Slowly he retraced his footsteps to where he had left the policeman searching the pavement for same clue which would identify the assailant of the night.

The constable was using a small electric lamp which he had taken from his pocket.

"Nothing here, sir," he said. "Only this bit of red paper."

Tarling took the small square of paper from the man's hand and examined it under the light of the lamp-a red square on which were written four words in Chinese: "He brought this trouble upon himself."

It was the same inscription as had been found neatly folded in the waistcoat pocket of Thornton Lyne that morning he was discovered lying starkly dead.

CHAPTER XIV

THE SEARCH OF MILBURGH'S COTTAGE

Mr. Milburgh had a little house in one of the industrial streets of Camden Town. It was a street made up for the most part of blank walls, pierced at intervals with great gates, through which one could procure at times a view of gaunt factories and smoky-looking chimney-stacks.

Mr. Milburgh's house was the only residence in the road, if one excepted the quarters of caretakers and managers, and it was agreed by all who saw his tiny demesne, that Mr. Milburgh had a good landlord.