For the next day or two, Sir Clinton's interest in the Hassendean case appeared to have faded out; and Inspector Flamborough, after following up one or two clues which eventually proved useless, was beginning to feel perturbed by the lack of direct progress which the investigation showed. Rather to his relief, one morning the Chief Constable summoned him to his office. Flamborough began a somewhat apologetic account of his fruitless investigations; but Sir Clinton cut him short with a word or two of appreciation of his zeal.
“Here's something more definite for you to go on,” he suggested. “I've just had a preliminary report from the London man whom we put on to search for the poison. I asked him to let me have a private opinion at the earliest possible moment. His official report will come in later, of course.”
“Has he spotted it, sir?” the Inspector inquired eagerly.
“He's reached the same conclusion as I did—and as I suppose you did also,” Sir Clinton assured him.
Flamborough looked puzzled.
“I didn't spot it myself,” he confessed diffidently. “In fact, I don't see how there was anything to show definitely what stuff it was, barring dilatation of the eye-pupils, and that might have been due to various drugs.”
“You should never lose an opportunity of exercising your powers of inference, Inspector. I mustn't rob you of this one. Now put together two things: the episode of the mixed melting-point and the phrase about his ‘triumph’ that young Hassendean wrote in his journal. Add the state of the girl's pupils as a third point—and there you are!”
Flamborough pondered for a while over this assortment of information, but finally shook his head.
“I don't see it yet, sir.”
“In that case,” Sir Clinton declared, with the air of one bestowing benevolence, “I think we'd better let it dawn on you slowly. You might be angry with yourself if you realised all of a sudden how simple it is.”