The doctor took the glass to the window, turned it upside down, and held it to the light. It was quite dry, quite clean. "Surely it's evident what happened," said Warrisden. "Chase came into the room, opened that cupboard door in the corner there. His keys are still dangling in the lock, he took the decanter and the tumbler out, placed them on the table at his side, sat down in his chair with the apple in his hand, leaned back and quietly died." "Yes, no doubt," said the doctor. "But I think here will be found the reason why he leaned back and quietly died," and he touched the decanter. "Opium poisoning. It may not have been an overdose, but a regular practice." He went to the door and called for Mrs. Wither. Mrs. Wither had now returned to the house. When she came upstairs into the room, he pointed to the decanter. "Did you ever see this before?" "No, sir," she answered. "Or that cupboard open?" "No, it was always locked." "Quite so," said the doctor. "You had better get some women to help you here," he went on; and, with Warrisden's assistance, he lifted Chase from the chair and carried him into his bedroom. "I must give notice to the police," he went on, and again he appealed to Warrisden. "Do you mind staying in the house till I come back?" "Not at all." The doctor locked the door of the room and took the key away with him. Warrisden waited with Princkley in the dining-room. The doctor had taken away the key. It seemed that his chance of discovering the secret which was of so much importance to Pamela and Millie Stretton and himself had vanished. If only he had come yesterday, or the day before! He sat down by the window and gazed out upon the street. A group of men and women were gathered in the roadway, looking up at the windows and talking quietly together. Then Princkley from behind said-- "Some letters came for Chase this morning. They were not taken up to his room. You had better look at them." Every one took him for a close friend. Princkley brought him the letters, and he glanced at the superscriptions lest any one should wear a look of immediate importance. He held the letters in his hand and turned them over one by one, and half-way through the file he stopped. He had come to a letter written upon thin paper, in a man's handwriting, with a foreign stamp upon the envelope. The stamp was a French one, and there was printed upon it: "Poste d'Algérie." Warrisden examined the post-mark. The letter came from Ain-Sefra. Warrisden went on with his examination without a word. But his heart quickened. He wondered whether he had found the clue. Ain-Sefra in Algeria. Warrisden had never heard of the place before. It might be a health resort, a wintering place. But this was the month of August. There would be no visitors at this time to a health resort in Algeria. He handed the letters back to Princkley.