After all, it was for the best—van Heerden could almost see the hand of Providence in this deliverance of his enemy into his power. There must be a settlement with Beale, that play-acting drunkard, who had so deceived him at first.

Dr. van Heerden could admire the ingenuity of his enemy and could kill him. He was a man whose mental poise permitted the paradox of detached attachments. At first he had regarded Stanford Beale as a smart police officer, the sort of man whom Pinkerton and Burns turn out by the score. Shrewd, assertive, indefatigable, such men piece together the scattered mosaics of humdrum crimes, and by their mechanical patience produce for the satisfaction of courts sufficient of the piece to reveal the design. They figure in divorce suits, in financial swindles and occasionally in more serious cases.

Van Heerden knew instinctively their limitations and had too hastily placed Beale in a lower category than he deserved. Van Heerden came to his workroom by way of the buffet which he had established for the use of his employees. As he shut the steel door behind him he saw Milsom standing at the rough wooden sideboard which served as bar and table for the workers.

"This is an unexpected pleasure," said Milsom, and then quickly, as he read the other's face: "Anything wrong?"

"If the fact that the cleverest policeman in America or England is at present on the premises can be so described, then everything is wrong," said van Heerden, and helped himself to a drink.

"Here—in the laboratory?" demanded Milsom, fear in his eyes. "What do you mean?"

"I'll tell you," said the other, and gave the story as he had heard it from Hilda Glaum.

"He's in the old passage, eh?" said Milsom, thoughtfully, "well there's no reason why he should get out—alive."

"He won't," said the other.

"Was he followed—you saw nobody outside?"

"We have nothing to fear on that score. He's working on his own."

Milsom grunted.

"What are we going to do with him?"

"Gas him," said van Heerden, "he is certain to have a gun."

Milsom nodded.

"Wait until the men have gone. I let them go at three—a few at a time, and it wants half an hour to that. He can wait. He's safe where he is. Why didn't Hilda tell me? I never even saw her."

"She went straight up from the old passage—through the men's door—she didn't trust you probably."

Milsom smiled wryly. Though he controlled these works and knew half the doctor's secrets, he suspected that the quantity of van Heerden's trust was not greatly in excess of his girl's.

"We'll wait," he said again, "there's no hurry and, anyway, I want to see you about old man Heyler."

"Von Heyler? I thought you were rid of him?" said van Heerden in surprise, "that is the old fool that Beale has been after. He has been trying to suck him dry, and has had two interviews with him. I told you to send him to Deans Folly. Bridgers would have taken care of him."

"Bridgers can look after nothing," said Milsom.

His eyes roved along the benches and stopped at a worker at the farther end of the room.

"He's quiet to-night," he said, "that fellow is too full of himself for my liking. Earlier in the evening before I arrived he pulled a gun on Schultz. He's too full of gunplay that fellow—excuse the idiom, but I was in the same tailor's shop at Portland Gaol as Ned Garrand, the Yankee bank-smasher."

Van Heerden made a gesture of impatience.

"About old Heyler," Milsom went on, "I know you think he's dangerous, so I've kept him here. There's a room where he can sleep, and he can take all the exercise he wants at night. But the old fool is restless—he's been asking me what is the object of his work."

"He's difficult. Twice he has nearly betrayed me. As I told you in the car, I gave him some experimental work to do and he brought the result to me—that was the sample which fell into Beale's hands."

"Mr. Beale is certainly a danger," said Milsom thoughtfully.

Van Heerden made a move toward the laboratory, but Milsom's big hand detained him.

"One minute, van Heerden," he said, "whilst you're here you'd better decide—when do we start dismantling? I've got to find some excuse to send these fellows away."

Van Heerden thought.

"In two days," he said, "that will give you time to clear. You can send the men—well, send them to Scotland, some out-of-the-way place where news doesn't travel. Tell them we're opening a new factory, and put them up at the local hotel."

Milsom inclined his head.

"That sounds easy," he said, "I could take charge of them until the time came to skip. One can get a boat at Greenock."

"I shall miss you," said van Heerden frankly, "you were necessary to me, Milsom. You're the driving force I wanted, and the only man of my class and calibre I can ever expect to meet, one who would go into this business with me."

They had reached the big vault and van Heerden stood regarding the scene of mental activity with something approaching complacency.

"There is a billion in process of creation," he said.

"I could never think in more than six figures," said Milsom, "and it is only under your cheering influence that I can stretch to seven. I am going to live in the Argentine, van Heerden. A house on a hill——"

The other shivered, but Milsom went on.

"A gorgeous palace of a house, alive with servants. A string band, a perfectly equipped laboratory where I can indulge my passion for research, a high-powered auto, wine of the rarest—ah!"

Van Heerden looked at his companion curiously.

"That appeals to you, does it? For me, the control of finance. Endless schemes of fortune; endless smashings of rivals, railways, ships, great industries juggled and shuffled—that is the life I plan."

"Fine!" said the other laconically.

They walked to a bench and the worker looked up and took off his mask.

He was an old man, and grinned toothlessly at van Heerden.

"Good evening, Signor Doctor," he said in Italian. "Science is long and life is short, signor."

He chuckled and, resuming his mask, returned to his work, ignoring the two men as though they had no existence.

"A little mad, old Castelli," said Milsom, "that's his one little piece—what crooked thing has he done?"

"None that I know," said the other carelessly; "he lost his wife and two daughters in the Messina earthquake. I picked him up cheap. He's a useful chemist."

They walked from bench to bench, but van Heerden's eyes continuously strayed to the door, behind which he pictured a caged Stanford Beale, awaiting his doom. The men were beginning to depart now. One by one they covered their instruments and their trays, slipped off their masks and overalls and disappeared through the door, upon which van Heerden's gaze was so often fixed. Their exit, however, would not take them near Beale's prison. A few paces along the corridor was another passage leading to the yard above, and it was by this way that Hilda Glaum had sped to the doctor's room.

Presently all were gone save one industrious worker, who sat peering through the eye-piece of his microscope, immovable.

"That's our friend Bridgers," said Milsom, "he's all lit up with the alkaloid of Enythroxylon Coca—— Well, Bridgers, nearly finished?"

"Huh!" grunted the man without turning.

Milsom shrugged his shoulders.

"We must let him finish what he's doing. He is quite oblivious to the presence of anybody when he has these fits of industry. By the way, the passing of our dear enemy"—he jerked his head to the passage door—"will make no change in your plans?"

"How?"

"You have no great anxiety to marry the widow?"

"None," said the doctor.

"And she isn't a widow yet."

It was not Milsom who spoke, but the man at the bench, the industrious worker whose eye was still at the microscope.

"Keep your comments to yourself," said van Heerden angrily, "finish your work and get out."

"I've finished."

The worker rose slowly and loosening the tapes of his mask pulled it off.

"My name is Beale," he said calmly, "I think we've met before. Don't move, Milsom, unless you want to save living-expenses—I'm a fairly quick shot when I'm annoyed."

Stanford Beale pushed back the microscope and seated himself on the edge of the bench.

"You addressed me as Bridgers," he said, "you will find Mr. Bridgers in a room behind that stack of boxes. The fact is he surprised me spying and was all for shooting me up, but I induced him to come into my private office, so to speak, and the rest was easy—he dopes, doesn't he? He hadn't the strength of a rat. However, that is all beside the point; Dr. van Heerden, what have you to say against my arresting you out of hand on a conspiracy charge?"

Van Heerden smiled contemptuously.

"There are many things I can say," he said. "In the first place, you have no authority to arrest anybody. You're not a police officer but only an American amateur."

"American, yes; but amateur, no," said Beale gently. "As to the authority, why I guess I can arrest you first and get the authority after."

"On what charge?" demanded Milsom, "there is nothing secret about this place, except Doctor van Heerden's association with it—a professional man is debarred from mixing in commercial affairs. Is it a crime to run a——"

He looked to van Heerden.

"A germicide factory," said van Heerden promptly.

"Suppose I know the character of this laboratory?" asked Beale quietly.

"Carry that kind of story to the police and see what steps they will take," said van Heerden scornfully. "My dear Mr. Beale, as I have told you once before, you have been reading too much exciting detective fiction."

"Very likely," he said, "but anyhow the little story that enthralls me just now is called the Green Terror, and I'm looking to you to supply a few of the missing pages. And I think you'll do it."

The doctor was lighting a cigarette, and he looked at the other over the flaring match with a gleam of malicious amusement in his eyes.

"Your romantic fancies would exasperate me, but for your evident sincerity. Having stolen my bride you seem anxious to steal my reputation," he said mockingly.

"That," said Beale, slipping off the bench and standing, hands on hips, before the doctor, "would take a bit of finding. I tell you, van Heerden, that I'm going to call your bluff. I shall place this factory in the hands of the police, and I am going to call in the greatest scientists in England, France and America, to prove the charge I shall make against you on the strength of this!"

He held up between his forefinger and thumb a crystal tube, filled to its seal with something that looked like green sawdust.

"The world, the sceptical world, shall know the hell you are preparing for them." Stanford Beale's voice trembled with passion and his face was dark with the thought of a crime so monstrous that even the outrageous treatment of a woman who was more to him than all the world was for the moment obliterated from his mind in the contemplation of the danger which threatened humanity.

"You say that the police and even the government of this country will dismiss my charge as being too fantastic for belief. You shall have the satisfaction of knowing that you are right. They think I am mad—but I will convince them! In this tube lies the destruction of all your fondest dreams, van Heerden. To realize those dreams you have murdered two men. For these you killed John Millinborn and the man PrÉdeaux. But you shall not——"

"Bang!"

The explosion roared thunderously in the confined space of the vault. Beale felt the wind of the bullet and turned, pistol upraised.