course there’s always that one question, the one nobody has ever been able to answer; of course I hardly expected to talk to you about it, but look.” There was the sound of a dining-room chair being moved; Mrs. Wright had clearly decided to settle down. “First,” she said, “she bought the arsenic.” “To kill rats,” Constance said to the teapot, and then turned and smiled at me. “To kill rats,” Uncle Julian said. “The only other popular use for arsenic is in taxidermy, and my niece could hardly pretend
So she did buy the poison .. Interesting theory !