"By the time she reached her own home reflection had shown her that there was one possible chance that Grell might not be guilty. She rang up the St. Jermyn's Club and asked for him. Fairfield answered, declaring that his friend was in the club, but busy--too busy to talk to the girl he was to marry next day, mark you. It is idle to suppose that she did not appreciate the excuse as a flimsy one--one manufactured perhaps for the purpose of an alibi. She must have gone to bed filled with foreboding. "All this is hypothesis. I am supposing that she never closely inspected the features of the dead man. The next morning she is informed that Grell was the victim. At once the lie that Fairfield told her assumed a new aspect. She denounced him as the murderer. She dared not say that she was the first to discover the body, for that would have meant revealing that she knew he was being blackmailed. "Then the Princess Petrovska paid her a visit and told her that Grell was not dead but in hiding. There was nothing for it, in default of any explanation, but to revert to the thought that he was the murderer. She went to extreme lengths to help him--even to forgery. She believes him guilty still; he believes her guilty." "But Petrovska?" objected Thornton. "I was coming to that. She is a clever woman. When Grell got in touch with her the following day she may have had many reasons for assisting him. She most likely had a shrewd idea of the situation and resolved to profit by it to avert suspicion. While Grell was suspected she would be safe. But it may have occurred to her that if we laid our hands on him and he told us anything, we might get on her track. Suppose that to be so, it is not difficult to see why she should take a prominent part in assisting him. She would still have a certain amount of money, for he paid her to come to England, and she, as we know, would stand at nothing." "It all sounds very interesting," commented the Assistant Commissioner, "but it looks to me as though it may be a tough proposition to get evidence bearing it out." Foyle pulled out his watch. "My idea may all tumble to pieces as soon as a test is applied. I can't pretend to be infallible. But we can try. I am going back to Scotland Yard now, sir. It is ten o'clock. I expect to be at it all night. Are you coming back?" "No, I don't think I can be of any assistance to you. I shall be glad if your theory does come out all right this time. The alternative suspicions are horrible. Good night, Mr. Foyle." CHAPTER LIII With his mind revolving the strength and weakness of his theory, Heldon Foyle returned to Scotland Yard. He paused for a moment at the door of the night-inspector's room. "Anything for me, Slack?" he asked. "Has Mr. Bolt come in? Ah, there you are, Bolt. Come down to my room." He led the way down the green corridor, the divisional inspector following. "Well?" asked the superintendent sharply, as he seated himself in his office.