"Well, she might, for one," suggested H.M. He sputtered behind his pipe. "Now, now, son, don't get your back up. I admit it's touché on that point. But, if she is his daughter, we got a valuable witness to Stone's credibility right under this roof."
Evelyn spoke thoughtfully. "What, by the way, do you think of Stone's theory of the murder?"
H.M. opened one eye.
"Stone's theory of the murder, hey? Ho ho ho. So he's got one too? You didn't include that, Ken. What is it?"
"Stone isn't satisfied with the idea that the strychnine and bromide bottles were switched; that fake labels were pasted over each, that Mrs. Antrim gave Hogenauer a dose of strychnine by mistake; and that afterwards the real murderer put the bottles back in their right places. He thinks it was a long-distance job, which the murderer wanted you to believe was managed from this house by someone who had access to the shelves. Stone's argument is that the murderer couldn't have known in advance what Antrim would prescribe…"
"Sound enough," said H.M. He seemed curiously intent. "Well?"
"He maintains that Mrs. Antrim gave Hogenauer an honest dose of bromide. The murderer, learning about this comes here and burgles the house. He fills up the big bromide container with real bromide he's bought at the chemist's; and then' he pinches a heavy dose of strychnine out of the poison-bottle. He put some sort of gummy substance on the real labels, and shoves the strychnine-bottle a little out of line. Later we are intended to assume (as Mrs. Antrim did assume) that the switching of bottles, and switching them back again, was done by somebody with free and easy access to the shelves. But actually it was done by an outsider from far away. Actually Hogenauer, by this theory, took home a harmless bottle of bromide. The change was effected next day, when the murderer called at Hogenauer's house… But Stone's theory is based on the idea that Keppel did the dirty. And we know that, whoever else it might have been, it wasn't Keppel."
H.M.'s disconcerting stare remained fixed. "I see," he growled softly.
"You see what? Did you think of it?"
"Oh, yes. Yes," he replied almost tenderly, "I did think of it; it was the very first thing I thought of. Uh-huh. It can't be overlooked. It jumps to the eye. It — anyhow, it may interest you to know that there's corroboration of that."