“That is a possible explanation, certainly,” my chief was good enough to respond. “We are dealing with one of those family tragedies which so seldom come to light. The ambitious man has married for money, as the girl has seen from the first, and the woman won’t see. Then he has found his wife in the way, and begun to neglect her. She, poor thing, has tried to hide the situation from her child, but Sarah has found it out for herself, and resented it. She has tried to open her mother’s eyes, and failed; or rather the mother has concealed the fact that she is no longer blind. Then in desperation, perhaps, the girl has gone secretly to work to obtain proof of her step-father’s infidelity, proof that will leave her mother no excuse for keeping her eyes shut any longer; that will compel her to leave the man....” The speech trailed off into a soliloquy, which became a silent one. Suddenly he stood up grasping in his hand a square glass bottle half full of pellets like those we had found on the corpse. “No need for further evidence of identity than this!” he exclaimed in triumph. “But this must be between you and me, Cassilis; I don’t think Charles can have been altogether satisfied with the theory that Weathered only carried these pellets to give to his enemies and this discovery makes it still less probable. He may have administered them for other purposes.” I shuddered at the hint. The Domino Club took on a darker shade in my imagination and I scarcely dared ask myself what horrors might have been concealed by those embroidered curtains that screened its Moorish alcoves. Tarleton slipped the glass bottle into his coat pocket, and locked the safe. Then he turned to survey the doctor’s table. “Now let us reconstruct the crime provisionally,” he said. “A patient of Weathered finds that he is in the doctor’s power and finds that Weathered is disposed to take some base advantage of him. He has seen the doctor recording his confession in a book, and he determines to release himself by getting hold of that book and destroying it. He is a member of the Domino Club; most likely he has been tempted or compelled to join it by Weathered. He may or may not know of these pellets and the purpose for which they are used. At all events he conceives the plan of drugging Weathered, obtaining his keys, and coming here to destroy the incriminating record. He carries out his purpose successfully, so far. But in his haste and excitement he overlooks one thing. And it is here.” For the life of me I could not repress a start as the consultant brought his hand down sharply on a small book that lay beside the inkstand on the writing-table. Little need to say what it was! The moment after Weathered’s appointment-book was lying open, and my chief’s keen eyes were rapidly searching the pages.