His remarks were checked by an exclamation from Roberts, who had regained some semblance of self-control while listening to Alan. "There was no accounting for what Paul would do," he stated, and all eyes turned to him, partly in curiosity, but more in unconcealed horror. "I may as well make my confession now as later," he sighed. "After I left Abbott's Lodge I motored to Upper Marlboro, deciding, as it was such a bad night, that I would remain at the hotel. It was before midnight when Corbin came in and told me that a letter had come that day from Canada from Zybinn and that he had taken it, with other papers, to the room Paul used as a sitting room. I gave Corbin his customary bribe--" "Cocaine," interposed Miriam quickly, and Roberts nodded. "I took Corbin's key to the front door," he went on, speaking with more of an effort, "and came back to find the letter which," turning with a scowl to Trenholm, "with your infernal astuteness, you divined bore a stamp code. You planted that letter and this trap--" "I did," admitted Trenholm quietly. "I realized that the thirteenth letter had not been read either by Paul or the person for whom the code was intended. Knowing that attempts had been made to steal something from this room, I judged that the letter had been lost here, and so"--with a quiet smile at Mrs. Nash--"I arranged to have the room vacated for an hour or two. I knew whoever would attempt to steal that letter had killed Paul." "But why?" demanded Doctor Nash. "Because the stamp code tells where Paul had secreted the Paltoff diamond." "It does!" Roberts was on his feet; his features distorted. "Good God! to think that I failed by so short a margin." "Sit down!" directed Trenholm, with a significant pressure on the physician's shoulder. "What did you do, Roberts, when you reached Abbott's Lodge on Monday night?" "I stole softly up here." Roberts moistened his parched lips. "I found the letter which Corbin had placed on the table and took up the nut pick, intending to open the envelope, take out the letter and leave it, and study the stamp code at my leisure at the hotel. A noise at my elbow caused me to glance around--Paul was standing at my side." "Well--what next?" prompted Trenholm, as Roberts ceased speaking. "My face must have betrayed me," he continued, a second later. "Paul's unexpected appearance shocked me out of my self-control. He turned, I suppose to call for help, and I drove the nut pick into his back." There was a pause which none cared to break. Roberts wiped some perspiration from his forehead and then spoke more rapidly.