“Captain Armstrong did me the honour to come to me some time ago, after his return from Sumatra. He had heard of me as a student of poisons, and he brought me a sample of one he had discovered.” “I know the one you mean, the toadstool that grows round the upas tree. Wasn’t that a wonderful discovery? I can tell you----” She checked herself rather sharply, and said no more. “I persuaded him to sell me all he had brought to England,” the specialist remarked, without appearing to notice anything. “But it has occurred to me since that he might have kept a little as a specimen, and if that is so, and you are disposed to part with it, I shall be glad.” Mrs. Baker eyed us with a touch of uneasiness, I thought. “I know I can trust you, Sir Frederick; and if Dr. Castle is your assistant I suppose I can trust him too. Dear Edgar did leave me a little bottleful, but he told me not to part with it to anyone, and not even to let anyone know I had it.” This was disconcerting news. I saw Tarleton’s thick eyebrows go up and down. “That was very sound advice,” he responded quietly. “However, your brother trusted me, as I have said, and I hope you can do the same. I shall be very greatly obliged if you will let me see the bottle.” The little woman got nimbly off the couch. “After all, it will be a relief to me to get rid of it,” she murmured. “I have always taken care to keep it under lock and key.” She produced a bunch of about two dozen keys from her pocket, all of them of that common design that will open each other’s locks with ease, and advanced to a chiffonier. “It is in here,” she informed us as she threw back the flimsy door and thrust her head inside. The next moment we heard a startled cry. “The bottle is gone!” CHAPTER XVI THE RED LIGHT Sir Frank and I both sprang to our feet to go to the chiffonier. But it was useless to turn over the rubbish it contained. The bottle of upasine was not there. And either the sister of the explorer was a very perfect actress or she was as much surprised as I was by its disappearance. “Whoever can have taken it?” she cried, gazing at us as if not quite certain that we were beyond suspicion of the theft. “Both my maids have been with me for years, and I have never missed anything before.” It was at moments like these that I most admired my chief. The encounter with a new perplexity seemed to afford him the keenest pleasure. He was like an angler who finds that he has hooked a trout where he only expected a chub. I could see from the knitting of his brows that he was already readjusting his ideas to this new factor in the case, and working out a different solution. His first step was to soothe the mistress of the house. “If you will allow me to help you I think we may be able to get on the track of the thief. Shall we sit down and talk it over quietly?”