These words produced a sudden, surprised silence. Guy broke it. “What do you mean, she didn't swallow it? She must have swallowed it!”
“Yes, I thought you didn't know quite as much about it as you pretended, Mr Matthews,” said Hannasyde. “The nicotine did not pass through the stomach. It was absorbed through the tissues of the mouth.” He held up the paper in his hand. “This is the analyst's report, which I've been waiting for. The medium through which your aunt was poisoned was a tube of toothpaste.”
“A-tube-of-toothpaste?” Guy repeated, blankly, and then was silent.
Hannasyde folded the report again, and put it away in his pocketbook. The deliberation of his movements seemed to fascinate Stella; her eyes followed them in a kind of numb bewilderment while a jumble of thoughts chased one another through her brain. These found expression presently in one sentence, blurted out unwarily. “Then anyone might have done it!”
“I don't think so, Miss Matthews.”
Mrs Matthews said with something of her usual smoothness: “Stella darling, just sit down and be quiet. You don't know anything about this, my dear child, and you must not keep on interrupting.” She turned towards Hannasyde, and said graciously: “You see now how absurd your suspicions were, Superintendent. We won't say any more about it, however. Naturally I understand that your duty compels you to suspect everybody. But this is most amazing news! A tube of toothpaste! You mean, I suppose, that the poison was injected into it. A hypodermic syringe, no doubt. I don't think that anyone in this house owns such a thing. It is a very, very terrible thought that my poor sister-in-law should have —”
Guy made an impatient gesture, as though to silence her. “How was it done?” he asked. “Are you at liberty to tell us that?”
“Certainly,” said Hannasyde. “The poison was in all probability injected, as your mother seems to have realised, by means of a hypodermic syringe, inserted into the bottom end of the tube, and driven up a little way through the paste. The paste at the bottom of the tube is untainted, and it is obvious that the paste at the top end must also have been free from poison.”
Guy said softly: “By Jove, that's clever! It might have been done at any time, then. Aunt Harriet has been working her way down the tube for days, till at last she reached the poison! Gosh!”
“It's awful!” Stella said. “It's devilish!”