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.

CHAPTER V

THE GREAT AQUEDUCT

The Birmingham reservoirs are a chain of lakes artificially produced by damming up the River Elan, a tributary of the Wye. The great aqueduct which carries the water from the Elan, eighty miles across country, travelling through hills and bridging valleys, runs past Ludlow and Cleobury Mortimer, through the Wyre Forest to Kidderminster, and on to Birmingham itself through Frankley, where there is a large storage reservoir from which the water is distributed.

The scenery was bleak and desolate. Before us the sun was sinking in a flood of crimson light. We walked briskly, the long legs of the Russian carrying him swiftly over the uneven ground while I trotted beside him. Before the last rays of the sun had died away we saw the black outline of the Caban Loch dam before us, and caught the sheen of water beyond. On the north lay the river Elan and on the south the steep side of a mountain towered up against the luminous sky. The road runs along the left bank of the river bounded by a series of bold and abrupt crags that rise to a height of some eight hundred feet above the level of the water. Just below the Caban Dam is a house occupied by an inspector in charge of the gauge apparatus that is used to measure the outflow of water from the huge natural reservoirs. The lights from his house twinkled through the growing darkness as we drew near, and we skirted it by a short detour and pressed on.

"How long does water take to get from here to Birmingham?" asked Sarakoff as we climbed up to the edge of the first lake.

"It travels about a couple of miles an hour," I replied. "So that means about a day and a half."

We spoke in low voices, for we were afraid of detection. The presence of two visitors at that hour might well have attracted attention.

"A day and a half! Then the bacillus has a long journey