“It could be.”  Rand was keeping one eye on the hall door and the other on the head of the spiral stairway.  “Don’t mention outside what I told you about Farnsworth having this brainstorm about Stephen Gresham.  If it got out, it might hurt Gresham professionally.  The fact is, Gresham has just retained me to investigate the Rivers murder for him.  That won’t interfere to any great extent with the work I’m doing here; if necessary, I’ll bring a couple of my men in from New Belfast to help me on the Rivers operation.”  He broke off abruptly, catching a movement at the head of the spiral, and lifted the pistol in his hand, as though showing it to Gladys.  “See,” he went on, “it has two hammers and two nipples, but only one barrel.  It was loaded with two charges, one on top of the other; the bullet of the rear charge acted as the breech-plug for the front charge....  Oh, Walters!” He affected to catch sight of the butler for the first time.  “Bring me that .36 Walch revolver, will you?”

“Yes, sir.”  Walters, crossing the room, veered to the right and went to the middle wall, bringing a revolver over to the desk.  It was a percussion weapon with an abnormally long cylinder.  “The cocktails are served,” he announced.

“We’ll be down in a moment; you can put these back where they belong when you find time,” Rand told him.  “Now, here,” he said to Gladys.  “This is the same idea, in a revolver.  Six chambers, two charges in each.  In theory, it was a good idea, but in actual practice ...”

Walters went out the hall door, presumably to call Varcek.  Rand continued talking about the superposed-load principle, as used in the Lindsay pistol and the Walch revolver, until he was sure the butler was out of hearing.  Gladys was looking at him in appreciative if slightly punch-drunk delight.

“I wondered why you brought that thing over here with you,” she said.  “Brother, was that a quick shift!...  You’re really sure he’s the one?”

“I’m not really sure of anything, except of my own existence and eventual extinction,” Rand told her.  “It pretty nearly has to be somebody inside this house.  I don’t think anybody else here, yourself included, would know enough about arms to rob this collection as selectively as it has been robbed.  Did you see what just happened, here?  I asked him for one of the most uncommon arms here, and he went straight and got it.  He knows this collection as well as your husband did, and I assume he knows values almost as well....  And, of course, there was a musket, too; Mr. Fleming didn’t collect long-arms, or he’d have had one.  It embodied the same principle as the pistol.  The legend is that this man Lindsay’s brother was a soldier; he was supposed to have been killed by Indians who drew the fire of the detail he was with and then charged them when their muskets were empty.”  Rand shrugged.  “Actually, the superposed-load principle is ancient; there’s a sixteenth-century wheel lock pistol in the Metropolitan Museum, in New York, firing two shots from the same barrel.”