"Ah, that is what I cannot quite make out, and there to my mind lies the only mystery in this case. On the 25th she was certainly in London, and it is not very likely that she would go back to Edinburgh in order to dispose of the jewels there, where they could most easily be traced."
"Not very likely, certainly," he assented drily.
"And," added the young girl, "on the day before she left for London, Lady Donaldson was alive."
"And pray," he said suddenly, as with comic complacency he surveyed a beautiful knot he had just twisted up between his long fingers, "what has that fact got to do with it?"
"But it has everything to do with it!" she retorted.
"Ah, there you go," he sighed with comic emphasis. "My teachings don't seem to have improved your powers of reasoning. You are as bad as the police. Lady Donaldson has been robbed and murdered, and you immediately argue that she was robbed and murdered by the same person."
"But—" argued Polly.
"There is no but," he said, getting more and more excited. "See how simple it is. Edith Crawford wears the diamonds one night, then she brings them back to Lady Donaldson's room. Remember the maid's statement: 'My lady said: "Have you put them back, my dear?"—a simple statement, utterly ignored by the prosecution. But what did it mean? That Lady Donaldson could not see for herself whether Edith Crawford had put back the jewels or not, since she asked the question."
"Then you argue—"
"I never argue," he interrupted excitedly; "I state undeniable facts. Edith Crawford, who wanted to steal the jewels, took them then and there, when she had the opportunity. Why in the world should she have waited? Lady Donaldson was in bed, and Tremlett, the maid, had gone.