"Sir Hilary just come in, sir," said some one, opening the door just wide enough to permit a head to be thrust within; but before Foyle could move the Assistant Commissioner himself walked in. "One moment, Sir Hilary," said the superintendent, and dashed out, to return again almost immediately. "I just wanted to make certain that we shouldn't be disturbed. There's a lot to tell you. Things have been happening." "So I gather," said the other, settling himself in the arm-chair. "You've got Grell, I hear. What's the next move? Do his finger-prints agree?" "They do not. He is not the murderer, but he won't say who is. The next move is, that I intend that to go in all the morning papers." He placed in Thornton's hand a copy of the typewritten paragraph, and the Assistant Commissioner read it slowly through. "I don't quite follow," he said as he handed it back. "It hints that Grell will be charged with the murder." "Exactly. It is intended to convey that impression. To tell you the truth, I have a piece of evidence of which I have not spoken to you before. It indicates a person possibly guilty whom we must not neglect. If she is guilty--which I half doubt--that paragraph may help us to get at the missing evidence." His voice sank to a whisper and he leaned forward with arms outspread over his desk. As he spoke, Thornton's voice changed. He leapt to his feet and brought his fist down vehemently on the desk. "I don't believe it, man!" he cried. "I don't believe it! It's incredible. You've made a mistake. It can't be. Why, you've believed it was Grell yourself all along. If you've made a mistake, then why not now?" Foyle's chin became a trifle aggressive. Thornton's astonishment was natural, but the superintendent did not like the appearance of lack of confidence. His blue eyes were alight. "You can draw your own inference from the facts, Sir Hilary," he said coldly. "I am clear in my mind. I have done nothing, because I want to make the evidence as to motive indisputable. Should I find I am wrong I shall, of course, write out my resignation." Thornton was not usually an impulsive man. He had recovered himself immediately upon his outburst and was once more calm and self-possessed. "Don't be offended, Foyle," he said, more mildly. "I beg your pardon. It was just a bit startling at first. We've been associated too long for misunderstanding. I'll back you up, and there's not going to be any talk of resignations." "Thank you, Sir Hilary," said the superintendent, entirely mollified. Going to the big safe he unlocked it and took something from the shelf which he handed to the Assistant Commissioner. The two bent over it. It was nearly two hours before the two concluded their task. Sir Hilary, his hands clasped behind his back, walked in deep thought back to his own room. Heldon Foyle put on his hat and coat and ordered a taxi. "Brixton Prison," he said to the driver. CHAPTER L