Average Jones crossed over and looked at the contrivance. Then his glance fell to a huge, old-fashioned keyhole below the new fastening. “You didn’t use that larger lock?” “No. I haven’t for months. The key is lost, I think.” Retracing his steps the investigator sighted the hole from the radiator, and shook his head. “It’s not in range,” he said. “Go on.” “As I reached the door on my return, I heard Rags yelp. You may believe I got to him quickly. He was pawing wildly at his nose. I called up the nearest veterinary. Within ten minutes the convulsions came on. The veterinary was here when Rags died, which was within fifteen minutes of the first spasm. He didn’t believe it was strychnine. Said the attacks were different. Whatever it was, I couldn’t find any trace of it in the stomach. The veterinary took the body away and made a complete autopsy.” “Did he discover anything?” “Yes. The blood was coagulated and on the upper lip he found a circle of small pustules. He agreed that both dogs probably swallowed something that was left in my office, though I don’t see how it could have got there.” “That won’t do,” returned Average Jones positively. “A dog doesn’t cry out when he swallows poison, unless it’s some corrosive.” “It was no corrosive. I examined the mouth.” “What about the radiator?” asked Average Jones, getting down on his knees beside that antiquated contrivance. “It seems to have been the center of disturbance.” “If you’re thinking of fumes,” replied the chemist. “I tested for that. It isn’t possible.” “No; I suppose not. And yet, there’s the curious feature that the fatal influence seems to have emanated from the corner which is the most remote from both windows and door. Are your windows left open at night?” “The windows, sometimes. The transom is kept double-bolted.” “Do they face any other windows near by?” “You can see for yourself that they don’t.” “There’s no fire-escape and it’s too far up for anything to come in from the street.” Average examined the walls with attention and returned to the big keyhole, through which he peeped. “Do you ever chew gum?” he asked suddenly. The Chemist stared at him. “It isn’t a habit of mine to,” he said. “But you wouldn’t have any objection to my sending for some, in satisfaction of a sudden irresistible craving?” “Any particular brand? I’ll phone the corner drug store.” “Any sort will suit, thank you.” When the gum arrived, Average Jones, after politely offering some to his host, chewed up a single stick thoroughly. This he rolled out to an extremely tenuous consistency and spread it deftly across the unused keyhole, which it completely though thinly, veiled. “Now, what’s that for?” inquired the chemist, eying the improvised closure with some contempt.