Then he said: “I begin to see the outline. Rich old man subject to heart attacks, likely to die of one, but doesn’t. Somebody wants him to die at once. Hydrogen chloride is introduced into a smelling-salts bottle; bottle is green and thus no one is likely to perceive its apparent emptiness or its actual content. Maid hands man smelling salts, when he is alone. He gets a good big sniff of it before he can stop himself—that’s bad, Susan. Think of the horrible pain—the shock—he dies really of the shock; his heart can’t stand it. Ordinarily I think a person might live for some hours, or even days, and be conscious. But the murderer counted on that bad heart and won. It looks like a natural death. Anyway it is a successful murder. Durrie has a studio where he seems to do chemical experiments. The nurse would know something of chemistry. But the murder would have been perfect if Miriam hadn’t suspected something. Which one did it?”

“It’s funny,” said Susan, “that you used the word a perfect murder. That very word is what started me thinking. Perfect. Too perfect!”

“Huh,” said Jim with vehemence.

“Too perfect. No one suspected it was murder. And that was the motive, you see. Murder had to be suspected.”

“Murder had to be—sorry, Susie, but I don’t see.”

“All right. Look at this. Durrie is in love with the nurse; wants to marry her. His uncle didn’t object. And there was no motive at all, remember, for murder—no money motive. No question of thwarted love. No motive at all except—m except that Rosina was a very willful young woman—and Miriam, no less willful, hated her.”

“But Miriam approved the marriage.”

“Oh, did she!” said Susan. “Then why were Rosina and Durrie obliged to steal meetings. In the garden at dusk. At midnight.”

“How do you know Rosina had gone downstairs to see Durrie?”

“I didn’t. But it’s a good reason. Name a better one.”

“Suppose she did,” conceded Jim. “What then?”

“Miriam had ruled that house and Durrie in the smallest detail for years. She loved her rule—a previous engagement of Durrie’s had been mysteriously broken off. The uncle was about to die anyway; here was a perfect plan to get rid of Rosina.”

“Do you mean Miriam murdered the old man? But that doesn’t make sense. She didn’t gain by it.”

“She did, Jim, if she could make Durrie think, in his heart, that it was murder. And that the newcomer, the nurse, was the only one who could have done it.”

“You can’t prove this, Susan, it’s mere theory. How do you know it was Miriam?”