"My dear fellow! consider. She had only to follow you in and see you safely into your seat and there you were, left till called for. She could then go home, make up for her part; draw out a plan of action, with the help, perhaps, of Mr. Weiss, provide herself with the necessary means and appliances and, at the appointed time, call and collect you."
"That is assuming a good deal," I objected. "It is assuming, for instance, that she lives within a moderate distance of Sloane Square. Otherwise it would have been impossible."
"Exactly. That is why I assume it. You don't suppose that she goes about habitually with lumps of prepared sugar in her pocket. And if not, then she must have got that lump from somewhere. Then the beads suggest a carefully prepared plan, and, as I said just now, she can hardly have been made-up when she met us in Kennington Lane. From all of which it seems likely that her present abode is not very far from Sloane Square."
"At any rate," said I, "it was taking a considerable risk. I might have left the theatre before she came back."
"Yes," Thorndyke agreed. "But it is like a woman to take chances. A man would probably have stuck to you when once he had got you off your guard. But she was ready to take chances. She chanced the railway, and it came off; she chanced your remaining in the theatre, and that came off too. She calculated on the probability of your getting tea when you came out, and she hit it off again. And then she took one chance too many; she assumed that you probably took sugar in your tea, and she was wrong."
"We are taking it for granted that the sugar was prepared," I remarked.
"Yes. Our explanation is entirely hypothetical and may be entirely wrong. But it all hangs together, and if we find any poisonous matter in the sugar, it will be reasonable to assume that we are right. The sugar is the Experimentum Crucis. If you will hand it over to me, we will go up to the laboratory and make a preliminary test or two."
I took the lump of sugar from my pocket and gave it to him, and he carried it to the gas-burner, by the light of which he examined it with a lens.
"I don't see any foreign crystals on the surface," said he; "but we had better make a solution and go to work systematically. If it contains any poison we may assume that it will be some alkaloid, though I will test for arsenic too. But a man of Weiss's type would almost certainly use an alkaloid, on account of its smaller bulk and more ready solubility. You ought not to have carried this loose in your pocket. For legal purposes that would seriously interfere with its value as evidence. Bodies that are suspected of containing poison should be carefully isolated and preserved from contact with anything that might lead to doubt in the analysis. It doesn't matter much to us, as this analysis is only for our own information and we can satisfy ourselves as to the state of your pocket. But bear the rule in mind another time."
We now ascended to the laboratory, where Thorndyke proceeded at once to dissolve the lump of sugar in a measured quantity of distilled water by the aid of gentle heat.