"I presume she left the car when I was stooping over cranking it," explained Nash. "She had arranged the heavy laprobes so that they gave the appearance of some one seated there." Nash waited for comment from his companions, but none forthcoming, he added, a trifle pettishly, "Betty's disappearance was a great shock, but I continued on my way to Washington, wondering what I should do. Then came the news of Paul's murder and I was positively staggered. And to be greeted before I reached Abbott's Lodge with Betty's piteous plea that I say nothing of our visit here on Monday night--why, it threw me entirely off my feet. For the sake of Betty--for the fair name of my wife's family--to save them from scandal--I kept silent." "And what has caused you to break that silence?" questioned Trenholm. "Only to you," in alarm, "and to Miss Ward. I must ask you to pledge your word not to speak of it outside." "And why have you told us?" "Because you are investigating Paul's murder and I feel that you should know all the facts of the case." Nash sighed. "I learned only this morning from a reliable source that Betty spent Monday night wandering about Abbott's Lodge and in the garage. She walked to Upper Marlboro in time to catch the milk train for Washington." "Who told you this, Doctor Nash?" asked Trenholm sternly. "I insist upon an answer." "Well, perhaps you should know--" somewhat doubtfully. "Corbin." Trenholm sat back and contemplated the clergyman. "Corbin," he repeated. "Thank you, Doctor Nash," as the latter rose. "How is your wife?" "Not so well." Nash's face clouded over. "I am going to stop and see her now," he said, and with a polite bow to Miriam, he left them. Trenholm waited until he was sure Nash had had time to reach the second floor before addressing Miriam. "You don't admire our reverend friend?" he asked, noting with secret amusement her wrathful expression. "I think he is horrid!" she ejaculated. "So--so slimy. And Mrs. Nash is so straightforward and absolutely sincere." Hastily she changed the subject. "How did that last code message read?" Trenholm looked carefully around before answering her, to be sure they were alone, then approaching close to her side, whispered it in her ear. "'Watch thirteenth letter. Suicides grave.'" "It sounds like gibberish," she murmured. "Do you still think it refers to the thirteenth letter of the alphabet?" "I do," firmly. "And quite appropriately so," he went on slowly, "when it commences such words as morphine, murder, madness--" "And Mason," she completed, quietly. "But, Mr. Trenholm, it's a poor rule that doesn't work both ways--" "What do you mean?" as she paused. "Counting the alphabet from A to M is thirteen," she said. "But counting from M to A the thirteenth letter is _A_." She looked at him queerly. "_Alexander_ Nash."