"And I'm afraid I can't follow your line of reasoning," Macklin said. He grinned suddenly. "I don't know why I should be raising problems for the police to worry about, when you're so convinced that you know just who did murder Helen Lathrup, and why!" "We know," Fenton said. "Then why don't you arrest him then?" "We intend to," Fenton said. "But first I'd like to point out the flaw in your line of reasoning. You've just said the flame started up again between Helen Lathrup and Darby, and she sat on Gerstle's exposé. That we know--Darby, as you say, has practically admitted it, because he knows it would remove any motive he might have had for killing Helen Lathrup. He'd have a very special reason for wanting her to stay alive. And he did want her to stay alive, you can be sure of that." "Not if she quarreled with him again still later," Macklin said. "Just have patience," Fenton said. "I'm coming to that. What makes you so sure she quarreled with him again, in a deadly serious way this time, and was going to expose him? We haven't uncovered a shred of evidence pointing in that direction. It just possibly might be true, because she was a quarrelsome woman, but even if it were true, he didn't kill her for that, or any other reason. He didn't kill her, period. If they had another quarrel, I rather suspect he'd have known how to talk himself back into her good graces again. So the whole quarrel motive is pure assumption on your part." "A very plausible assumption," Macklin pointed out. "Under ordinary circumstances it would be," Fenton conceded. "But it carries no weight at all now, because we know who murdered Helen Lathrup and--well, we can make a pretty good guess as to why he did it, even if we're not absolutely sure about his motive." Fenton nodded, his lips tightening a little. "By the same token, we know that Darby couldn't have murdered her. He happens to have an unbreakable alibi for that particular morning, and the two hoodlums who kidnapped Hansen have just as good an alibi, and they were the only professional, gun-carrying characters in his employ, as far as we've been able to determine. But Darby couldn't have murdered her anyway--because someone else did. Someone else went into her office and shot her dead and it was _that_ which started the fire under Darby. With Lathrup dead, Darby had no longer a beautiful, protective, guardian angel--or crime-blinking witch, if you'd prefer that term--to keep the exposé under wraps, and Gerstle would have had a field day. And Gerstle was going ahead with it, not telling anyone, not even Mr. Eaton or Hansen here ... although Darby made the mistake of thinking Hansen did know and had him kidnapped also, to silence him." Macklin shook his head. "I'm sorry, Lieutenant. I just can't buy it. I'm willing to be convinced, of course, if you've strong evidence to support it. But otherwise--"