"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.