What, he asked himself, must have been the motive for such a crime? Certainly not merely to gratify a feeling of hate. The motive undoubtedly was to enable the survivor to claim Phyllis as his wife and to live with her in good social standing and without fear of his rival. But the crime, French reminded himself, had a peculiar feature. The staged accident on the moor involved the disappearance of _both_ actors, the murderer as well as the victim. If, then, the murderer disappeared, he could not live with Phyllis. If either Berlyn or Pyke were guilty, therefore, he had carried out the crime in a way which robbed him of the very results for which he had committed it. French saw that he was up against a puzzling dilemma. If Berlyn had murdered Pyke, it was unlikely that Mrs. Berlyn would have assisted. If, on the other hand, Pyke had murdered Berlyn, Mrs. Berlyn’s action was clear, but not Pyke’s, for Pyke could get nothing out of it. French swore bitterly as he realised that in all probability his former view of the case was incorrect and that he was once again without any really satisfactory theory on which to work. Nor did some hours’ thought point the way to a solution of his problem. At least, however, he saw his next step. Mrs. Berlyn was the accomplice of _some one_. That some one was doubtless alive and biding his time until he thought it safe to join the lady. If so, she was pretty sure to know his whereabouts. Could she be made to reveal it? French thought that if in some way he could give her a thorough fright, she might try to get a warning through. It would then be up to him to intercept her message, which would give him the information he required. This meant London. He slept the night in Plymouth, and next day, which was Saturday, travelled up to Paddington. Chapter Seventeen “Danger!” Before leaving Plymouth French had wired to Mrs. Berlyn, asking for an interview for the following Monday morning. On reaching the Yard he found a reply. If he called round about half past ten the lady would see him. He rang his bell for Sergeant Carter. “I shall want you with me to-day, Carter,” he explained. “Have a taxi ready at ten-fifteen.” As they were driving toward Chelsea he explained the business. “It’s to help me to shadow a woman, a Mrs. Phyllis Berlyn. Lives at 70b Park Walk. There’s her photograph. When I go in, you keep this taxi and be ready to pick me up when I want you.” If he were to tap a possible S O S, he must begin by finding out if his victim had a telephone. He therefore got out at the end of Park Walk, and passing the house, turned into an entry leading to the lane which ran along behind the row. The absence of wires front and rear showed that the house was not connected up. Then he went to the door and knocked. Mrs. Berlyn received him at once.