The prisoner smiled as he saw Foyle carefully shift his chair to guard against any sudden rush, before turning his back. He was a moment preparing the materials and then placed a blank sheet of paper on a little table in front of Grell. "Will you kindly hold out your hands?" he said. As Grell did so he smeared the tips of the fingers of the right hand with ink. "Now press your fingers lightly but firmly on the paper. Thank you." He brought a little standard lamp closer, and under its rays studied the two sets of prints closely. He did not need a magnifying-glass to see that none of Grell's finger-marks agreed with the two that were clear on the dagger. Grell leaned back in his chair as though the matter were one of complete indifference to him. "Does that satisfy you, Mr. Foyle?" he asked at last. The superintendent nodded as their eyes met. "It satisfies me that you did not actually kill the man," he said steadily. "I'll own I'm not surprised at that. I believe if you had killed him you would have been man enough to have stayed and faced the consequences. You will observe that I have not formally arrested you yet. But I do believe that you know all about the crime--that you were perhaps an eye-witness." For the first time during the interview Robert Grell lost hold of his self-control. His fists clenched and the steel of the handcuffs bit deep into his wrists as he momentarily forgot that he was handcuffed. There was a meaning in Foyle's tone that he could not fail to understand. He caught at his breath once or twice and his temples flamed scarlet. "Speak plainly now!" he cried hoarsely. "What are you hinting at?" Slowly Heldon Foyle began to tear the sheet of paper bearing Grell's finger-marks into minute fragments. He was calm, inscrutable. "I thought I made myself clear," he replied. "To make it plainer I will ask you if a man, famous, rich, and with an honourable reputation, flies on the eve of his wedding-day, assisted by his valet, hides himself in a low part of London, and associates with doubtful characters, whose friends abduct and drug police officers, who uses, in short, every effort to avoid or to hamper justice--has not some strong reason for his actions? Is it not plausible to suppose that he is an accessory either before or after the fact?" Grell sighed as if in relief, and, stooping, picked up his cigar, which had fallen on the carpet. He had recovered his calm. "You are a better judge of evidence than I am," he said unemotionally. "Personally, I don't think the facts you have mentioned would convict me of anything but eccentricity. Who is this Harry Goldenburg, anyway? Beyond the fact that he's my double I know nothing of him. That's certainly a coincidence, but why on earth I should conceal anything I know is beyond me."