“Now that’s done, Mr. Cheyne, we’ll prove our confidence in you by showing you the cipher. But first perhaps you would write to Miss Merrill. Also if any point is not quite clear to you please do not hesitate to question us.” Cheyne was by no means enamored of the way things had turned out. He had been forced into an association with men with whom he had little in common and whom he did not trust. Had it not been for the trump card they held in the person of Joan Merrill nothing would have induced him to throw in his lot with them. But now, contingent on their good faith to him, he had pledged his word, and though he was not sure how far an enforced pledge was binding, he felt that as long as they kept their part of the bargain, he must keep his. He therefore wrote his letter, and then turning to Blessington, answered him civilly: “There is one thing I should like to know; I have thought about it many times. How did you drug me in that hotel in Plymouth without my knowledge and without leaving any traces in the food?” Blessington smiled. “I’ll tell you that with pleasure, Mr. Cheyne,” he answered readily, “but I confess I am surprised that a man of your acumen was puzzled by it. It depended upon prearrangement, and given that, was perfectly simple. I provided myself with the drug—if you don’t mind I won’t say how, as I might get someone else into trouble—but I got a small phial of it. I also took two other small bottles, one full of clean water, the other empty, together with a small cloth. Also I took my Extra Special Flask. Sime, like a good fellow, get my flask out of the drawer of my wrecked escritoire.” He smiled ruefully at Cheyne. “Then I prepared for our lunch: the private room, the menu and all complete. I told them at the hotel we had some business to arrange, and that we didn’t want to be disturbed after lunch. You know, of course, that I got all details of your movements from Miss Dangle?” “Yes, I understand that.” As Cheyne spoke Sime re-entered the room, putting down on the table the flask which had figured in the scene at the hotel. Blessington handed it to Cheyne. “Examine that flask, Mr. Cheyne,” he invited. “Do you see anything remarkable about it?” It seemed an ordinary silver pocket flask, square and flat, and with a screw-down silver stopper. It was chased on both sides with a plain but rather pleasing design, and the base was flat so that it would stand securely. But Cheyne could see nothing about it in any way unusual. “Open it,” Blessington suggested. Cheyne unscrewed the stopper and looked down the neck, but except that there was a curious projection at one side, which reduced the passage down to half the usual size, it seemed as other flasks. Blessington laughed. [Illustration: Two diagrams of a flask, divided down the middle and containing liquids in both parts. In the second diagram, the flask is tipped, and liquid pours from the right half only.]