een before,
though it was my old beat 'afore I went to Birmingham. O' course it may
be because I been out o' London a spell. But blest if I ever seed so
many fine shop windows in Regent Street before, or so many different
colours."

"Headache?"

"Bless you, no, sir. Just the opposite, if you understand." He looked
round suddenly. "What's that noise?" he asked. "It's been worryin' me
since I came in here."

We listened intently, but neither I nor Sarakoff could hear anything.

"It comes from there." The man pointed to the laboratory door. I went
and opened it and stood listening. In a corner by the window a
clock-work recording barometer was ticking with a faint rhythm.

"That's the noise," said the man from Birmingham. "I knew it wasn't no
clock, 'cause it's too fast."

Sarakoff glanced significantly at me.

"All the senses very acute," he said. "At least, hearing and seeing." He
took a bottle from the laboratory and uncorked it in one corner of the
study. "Can you smell what this is?"

The man, sitting ten feet away, gave one sniff.

"Ammonia," he said promptly, and sneezed. "This 'ere Blue Disease," said
the man after a long pause, "is it dangerous?"

He spread out his fingers, squeezing the turquoise nails to see if the
colour faded. He frowned to find it fixed. I was standing at the window,
my back to the room and my hands twisting nervously with each other
behind me.

"No, it is not dangerous," said Sarakoff. He sat on the edge of the
writing-table, swinging his legs and staring meditatively at the floor.
"It is not dangerous, is it, Harden?"

I replied only with a jerky, impatient movement.

"What I mean," persisted the man, "is this--supposin' the police arrest
me, when I go back to my job. 'Ave they a right? 'Ave people a right to
give me the shove--to put me in a 'orspital? That crowd round me in the
street--it confused me, like--as if I was a leper." He paused and looked
up at Sarakoff enquiringly. "What's the cause of it?"

"A germ--a bacillus."

"Same as what gives consumption?"

Sarakoff nodded. "But this germ is harmless," he added.

"Then I ain't going to die?"

"No. That's just the point. You aren't going to die," said the Russian
slowly. "That's what is so strange."

I jumped round from the window.

"How do you know?" I said fiercely. "There's no proof. It's all theory
so far. The calculations may be wrong."

The man stared at me wonderingly. He saw me as a man fighting with