"We cannot go all the way by taxi. Tell the man to drive to Baker Street," she said.

She spoke no word during the journey, nor was Beale inclined for conversation. At Baker Street Station they stopped and the cab was dismissed. Together they walked in silence, turning from the main road, passing the Central Station and plunging into a labyrinth of streets which was foreign territory to the American.

It seemed that he had passed in one step from one of the best-class quarters of the town to one of the worst. One minute he was passing through a sedate square, lined with the houses of the well-to-do, another minute he was in a slum.

"The place is at the end of this street," she said.

They came to what seemed to be a stable-yard. There was a blank wall with one door and a pair of gates. The girl took a key from her bag, opened the small door and stepped in, and Beale followed.

They were in a yard littered with casks. On two sides of the yard ran low-roofed buildings which had apparently been used as stables. She locked the door behind her, walked across the yard to the corner and opened another door.

"There are fourteen steps down," she said, "have you a light of any kind?"

He took his electric torch from his pocket.

"Give it to me," she said, "I will lead the way."

"What is this place?" he asked, after she had locked the door.

"It used to be a wine merchant's," she said shortly, "we have the cellars."

"We?" he repeated.

She made no reply. At the bottom of the steps was a short passage and another door which was opened, and apparently the same key fitted them all, or else as Beale suspected she carried a pass key.

They walked through, and again she closed the door behind them.

"Another?" he said, as her light flashed upon a steel door a dozen paces ahead.

"It is the last one," she said, and went on.

Suddenly the light was extinguished.

"Your lamp's gone wrong," he heard her say, "but I can find the lock."

He heard a click, but did not see the door open and did not realize what had happened until he heard a click again. The light was suddenly flashed on him, level with his eyes.

"You can't see me," said a mocking voice, "I'm looking at you through the little spy-hole. Did you see the spy-hole, clever Mr. Beale? And I am on the other side of the door." He heard her laugh. "Are you going to arrest the doctor to-night?" she mocked. "Are you going to discover the secret of the Green Rust--ah! That is what you want, isn't it?"

"My dear little friend," said Beale smoothly, "you will be very sensible and open that door. You don't suppose that I came here alone. I was shadowed all the way."

"You lie," she said coolly, "why did I dismiss the cab and make you walk? Oh, clever Mr. Beale!"

He chuckled, though he was in no chuckling mood.

"What a sense of humour!" he said admiringly, "now just listen to me!"

He made one stride to the door, his revolver had flicked out of his hip-pocket, when he heard the snap of a shutter, and the barrel that he thrust between the bars met steel. Then came the grind of bolts and he pocketed his gun.

"So that's that," he said.

Then he walked back to the other door, struck a match and examined it.

It was sheathed with iron. He tapped the walls with his stick, but found nothing to encourage him. The floor was solidly flagged, the low roof of the passage was vaulted and cased with stone.

He stopped in his search suddenly and listened. Above his head he heard a light patter of feet, and smiled. It was his boast that he never forgot a voice or a footfall.

"That's my little friend on her way back, running like the deuce, to tell the doctor," he said. "I have something under an hour before the shooting starts!"

CHAPTER XXIII

AT THE DOCTOR'S FLAT

Dr. van Heerden did not hurry his departure from his Staines house. He spent the morning following Oliva's marriage in town, transacting certain important business and making no attempt to conceal his comings and goings, though he knew that he was shadowed. Yet he was well aware that every hour that passed brought danger nearer. He judged (and rightly) that his peril was not to be found in the consequences to his detention of Oliva Cress well.

"I may have a week's grace," he said to Milsom, "and in the space of a week I can do all that I want."

He spent the evening superintending the dismantling of apparatus in the shed, and it was past ten o'clock on Tuesday before he finished.

It was not until he was seated by Milsom's side in the big limousine and the car was running smoothly through Kingston that he made any further reference to the previous afternoon.

"Is Beale content?" he asked.

"Eh?"

Milsom, dozing in the corner of the car, awoke with a start.

"Is Beale content with his prize--and his predicament?" asked van Heerden.

"Well, I guess he should be. That little job brings him a million. He shouldn't worry about anything further."

But van Heerden shook his head.

"I don't think you have things quite right, Milsom," he said. "Beale is a better man than I thought, and knows my mind a little too well. He was astounded when Homo claimed to be a priest--I never saw a man more stunned in my life. He intended the marriage as a bluff to keep me away from the girl. He analysed the situation exactly, for he knew I was after her money, and that she as a woman had no attraction for me. He believed--and there he was justified--that if I could not marry her I had no interest in detaining her, and engaged Homo to follow him around with a special licence. He timed everything too well for my comfort."

Milsom shifted round and peered anxiously at his companion.

"How do you mean?" he asked. "It was only by a fluke that he made it in time."

"That isn't what I mean. It is the fact that he knew that every second was vital, that he guessed I was keen on a quick marriage and that to forestall me he carried his (as he thought) pseudo-clergyman with him so that he need not lose a minute: these are the disturbing factors."

"I don't see it," said Milsom, "the fellow's a crook, all these Yankee detectives are grafters. He saw a chance of a big rake off and took it, fifty-fifty of a million fortune is fine commission!"

"You're wrong. I'd like to think as you do. Man! Can't you see that his every action proves that he knows all about the Green Rust?"