"That can wait for a minute. Go on with what you are saying."
"Well — it's not much." He rubbed his leathery jaw, and at that moment he looked older than Stone. "Sometimes I used to drop in on Keppel, at his invitation. He wasn't a recluse like the other one. I liked to hear him talk. Ever see him in action? Little chap standing up very straight, eyes half-shut, two fingers pinched together in the air as though he'd got hold of an idea by the tail. Fussy, bustling sort. But I liked him. He could talk on the subject of Light (that was his branch); you didn't know quite what he was talking about, but it sounded damn interesting with all those thingummyjigs. Understand? Oh, ah, well.
"This afternoon he rang me up and asked me if I could come over here. That was about four o'clock. When I got here he said he wanted `expert advice.' I said, on what? Then he showed this envelope. The flap was gummed down, but there was no red seal on it. Then he said, `I want to put this envelope in such a position that nobody who came in here secretly could possibly get at its contents.' "
"Yes?" I prompted, as he paused.
"Naturally, I said, `why don't you lock it up in the hotel safe? Are you afraid of burglars?' He said I didn't understand. He's got a very patient air, though his English gets mixed up when he's excited. He said something to the effect that this was a kind of trap. He said he wanted to make certain nobody could put over any hanky-panky on him: move the letter: read it: touch it. He said he'd got some lamp-black to spread in such a position that if the letter were moved at all there'd be traces. I showed him another trick. See this?"
He held out the envelope and pointed to the seal. We all crowded round. Evelyn had ducked into her own room, to put on her shoes and tidy herself up; but at this she emerged like a cuckoo out of a clock.
"What about it?" Stone asked suspiciously. "I don't see anything. It looks like a blob of plain wax to me. Hold on! It's a finger-print."
"It's Keppel's finger-print," Murchison told him with dour complacency. "There are ways of forging seals, but you can't do any bread-crumb trick that will imitate this. It's too delicate. Well, I put the envelope into the pigeon-hole and arranged it for him. Then I asked what the game was. He said if I would come round the next morning he would tell me. That was all."
"But the strychnine?"
Murchison swore under his breath. "There's the worst of it. I said, `Are you going to wait up to catch somebody at that envelope?' He said that he'd probably be asleep. I said, `asleep?' Then he got out a yellowish envelope with a dose of white powder in it, and showed it to me. I remember his exact words, because he was so precise about 'em. He said: