One night, just as I entered my house, the telephone bell in the hall rang sharply. I picked up the receiver impatiently, for I was tired with the long day's work.

"Is that Dr. Harden?"

"Yes."

"Can you come down to Charing Cross Station at once? The station-master is speaking."

"An accident?"

"No. We wish you to identify a person who has arrived by the boat-train. The police are detaining him as a suspect. He gave your name as a reference. He is a Russian."

"All right. I'll come at once."

I hung up the receiver and told the servant to whistle for a taxi-cab. Ten minutes later I was picking my way through the crowds on the platform to the station-master's office. I entered, and found a strange scene being enacted. On one side of a table stood Sarakoff, very flushed, with shining eyes, clasping a black bag tightly to his breast. On the other side stood a group of four men, the station-master, a police officer, a plain clothes man and an elderly gentleman in white spats. The last was pointing an accusing finger at Sarakoff.

"Open that bag and we'll believe you!" he shouted.

Sarakoff glared at him defiantly.

I recognized his accuser at once. It was Lord Alberan, the famous Tory obstructionist.

"Anarchist!" Lord Alberan's voice rang out sharply. He took out a handkerchief and mopped his face.

"Arrest him!" he said to the constable with an air of satisfaction. "I knew he was an anarchist the moment I set eyes on him at Dover. There is an infernal machine in that bag. The man reeks of vodka. He is mad."

"Idiot," exclaimed Sarakoff, with great vehemence. "I drink nothing but water."

"He wishes to destroy London," said Lord Alberan coldly. "There is enough dynamite in that bag to blow the whole of Trafalgar Square into fragments. Arrest him instantly."

I stepped forward from the shadows by the door. Sarakoff uttered a cry of pleasure.

"Ah, Harden, I knew you would come. Get me out of this stupid situation!"

"What is the matter?" I asked, glancing at the station-master. He explained briefly that Lord Alberan and Sarakoff had travelled up in the same compartment from Dover, and that Sarakoff's strange restlessness and excited movements had roused Lord Alberan's suspicions. As a consequence Sarakoff had been detained for examination.

"If he would open his bag we should be satisfied," added the station-master. I looked at my friend significantly.

"Why not open it?" I asked. "It would be simplest."

My words had the effect of quieting the excited professor. He put the bag on the table, and placed his hands on the top of it.

"Very well," he said slowly, "I will open it, since my friend Dr. Harden has requested me to do so."

"Stand back!" cried Lord Alberan, flinging out his arms. "We may be so much dust flying over London in a moment."

Sarakoff took out a key and unlocked the bag. There was silence for a moment, only broken by hurrying footsteps on the platform without. Then Lord Alberan stepped cautiously forward.

He saw the worn canvas lining of the bag. He took a step nearer and saw a wooden rack, fitted in the interior, containing six glass tubes whose mouths were stopped with plugs of cotton wool.

"You see, there is nothing important there," said Sarakoff with a smile. "These objects are of purely scientific interest." He took out one of the tubes and held it up to the light. It was half full of a semi-transparent jelly-like mass, faintly blue in colour. The detective, the policeman and the station official clustered round, their faces turned up to the light and their eyes fixed on the tube. The Russian looked at them narrowly, and reading nothing but dull wonderment in their expressions, began to speak again.

"Yes—the Bacillus Pyocyaneus," he said, with a faint mocking smile and a side glance at me. "It is occasionally met with in man and is easily detected by the blue bye-product it gives off while growing." He twisted the tube slowly round. "It is quite an interesting culture," he continued idly. "Do you observe the uniform distribution of the growth and the absence of any sign of liquefaction in the medium?"

Lord Alberan cleared his throat.

"I—er—I think we owe you an apology," he said. "My suspicions were unfounded. However, I did my duty to my country by having you examined. You must admit your conduct was suspicious—highly suspicious, sir!"

Sarakoff replaced the tube and locked the bag. Lord Alberan marched to the door and held it open.

"We need not detain you, sir," said the detective. The policeman squared his shoulders and hitched up his belt. The station official looked nervous.

Dr. Sarakoff, with a gesture of indifference, picked up the bag and, taking me by the arm, passed out on to the brilliantly-lit platform. "Pyocyaneus," he muttered in my ear; "pyocyaneus, indeed! Confound the fellow. He might have got me into no end of trouble if he had known the truth, Harden."

"But what is it?" I asked. "What have you got in the bag?"

He stopped under a sizzling arc-lamp outside the station.

"The bag," he said touching the worn leather lovingly, "contains six tubes of the Sarakoff-Harden bacillus. Yes, I have added your name to it. I will make your name immortal—by coupling it with mine."

"But what is the Sarakoff-Harden bacillus?" I cried.

He struck an attitude under the viperish glare of the lamp and smiled. He certainly did look like an anarchist at the moment. He loomed over me, huge, satanic, inscrutable.

A thrill, almost of fear, passed over me. I glanced round in some apprehension. Under an archway near by I saw Lord Alberan looking fixedly at us. The expression of suspicion had returned to his face.

"You mean——?" He nodded. I gulped a little. "You really have——?" He continued to nod. "Then we can try the great experiment?" I whispered, dry throated."At once!" The detective passed us, brushing against my shoulder. I caught Sarakoff by the arm.

"Look here—we must get away," I muttered. I felt like a criminal. Sarakoff clasped the bag firmly under his free arm. We began to walk hurriedly away. Our manner was furtive. Once I looked back and saw Alberan talking, with excited gestures, to the detective. They were both looking in our direction. The impulse to run possessed me. "Quick," I exclaimed, "there's a taxi. Jump in. Drive to Harley Street—like the devil."

Inside the cab I lay back, my mind in a whirl.

"We begin the experiment to-morrow," said Sarakoff at last. "Have you made plans as I told you?"

"Yes—yes. Of course. Only I never believed it possible." I controlled myself and sat up. "I fixed on Birmingham. It seemed best—but I never dreamed——"

"Good!" he exclaimed. "Birmingham, then!"

"Their water supply comes from Wales."

We spoke no more till I turned the key of my study door behind me. It was in this way that the germ, which made so vast and strange an impression on the course of the world's history, first reached England. It had lain under the very nose of Lord Alberan, who opposed everything new automatically. Yet it, the newest of all things, escaped his vigilance.

We decided to put our plans into action without delay, and next morning we set off, carrying with us the precious tubes of the Sarakoff-Harden bacillus. Throughout the long journey we scarcely spoke to each other. Each of us was absorbed in his picture of the future effects of the germ.

There was one strange fact that Sarakoff had told me the night before, and that I had verified. The bacillus was ultra-microscopical—that is, it could not be seen, even with the highest power, under the microscope. Its presence was only to be detected by the blue stain it gave off during its growth.