Mortality.
There was a great deal of activity near the point at which the men stood. Drills and rock cutters had formed three sides of an enclosure in a ridge of solid rock, and now a giant crane was lowering thick slabs of metal to form the walls. Nearby, waiting to be placed, lay the slab which would obviously become the door to whatever Sam was building. Its surface was entirely smooth, but it bore great hinges and some sort of a locking device was built in along one edge.
Carter Hagen watched the activity and considered Sam's reply to his question. "Then this is to be a mausoleum?"
Sam chuckled. "Only in a sense. Not a place to house my dead bones if that's what you mean."
Carter Hagen, understanding this lonely old man as he did, knew further questions would be useless. Sam was like that. If he wanted you to know something, he told you.
So Carter held his peace and they returned to the mansion where Sam gave him a drink after they concluded the business he had come on.
Sam also gave Carter something else—an envelope. "Put that in your safe, Carter. You're comparatively young. I'm taking it for granted you will survive me."
"And this is—?"
"My will. All old men should leave wills and I'm no exception to the rule. When I'm dead, open it and read what's inside."