“By Jove!” said he, somewhat awed. “You can reason, young man.”

“I’ve got to, reason a lot further, if I’m to get anywhere in this affair,” said Average Jones with conviction. “Do you care, to come to Galvin’s Alley with me?”

Together they went down the hill to a poor little house, marked by white crêpe. The occupants were Italians who spoke some English. They said that four-year-old Pietro had been playing around a woodpile the afternoon before, when he was taken sick and came home, staggering. The doctor could do nothing. The little one passed from spasm into spasm, and died in an hour.

“Was there a mark like a ring anywhere on the hand or face?” asked Average Jones.

The dead child’s father looked surprised. That, he said, was what the strange gentleman who had come that very morning asked, a queer, bent little gentlemen, very bald and with big eye-glasses, who was kind, and wept with them and gave them money to bury the “bambino.”

“Moseley, by the Lord Harry!” exclaimed Mr. Curtis Fleming. “But what was the death-agent?”

Average Jones shook his head. “Too early to do more than guess. Will you take me to Professor Moseley’s place?”

The old house stood four-square, with a patched-up conservatory on one wing. In the front room they found the recluse’s body decently disposed, with an undertaker’s assistant in charge. From the greenhouse came a subdued hissing.

“What’s that?” asked Jones.

“Fumigating the conservatory. There was a note found near the body insisting on its being done. ‘For safety,’ it said, so I ordered it looked to.”