never know. Even professional criminals get careless and he isn't a professional. It's surprising how often intruders leave traces somewhere. They get careless and drop something, even a slip of paper with a name or address on it. I know a detective lieutenant who's firmly convinced you have at least a forty percent chance of tracing a criminal intruder if you're thorough enough and explore all of the possibilities." "All right, David, go ahead. I won't try to stop you. Find out all you can. I think you're wrong. I don't believe it was a prank. I'm sure it was something stranger and more terrifying, something we can't even begin to understand. But I don't want you to blame me later. Although I really can't see what good catching him would do." "You don't? I should think you'd be the first to understand how I feel." "I can understand how you feel, David. But what good would knocking him down do? If you're right about its being a prank he's a very sick man. Actually, you ought to have compassion and want to help him." "I'm afraid I can't be that objective about it. It's a matter of male pride." "Well, go ahead, indulge your pride, David. I'm not stopping you...." The parting shot rankled a little as David stood outside the apartment building staring down the long length of MacDougal Street, his eyes alert for a cruising taxi. Simply being angry with her made no sense at all, he told himself. A woman couldn't understand how a man felt when he was caught up in an ugly situation that could only be straightened out in one way if he wanted to go on living with himself. Being angry made no sense, but he should have explained to her exactly what would happen to his integrity if he shrugged the whole matter off and forgot about it. Emotionally she would never understand, but he should have made a serious effort to at least straighten her out intellectually and correct the impression he'd left with her that he was scientifically moronic and still living in the Middle Ages as far as mental illness was concerned. The prankster was quite possibly psychotic, or, at the very least, a psychopathic personality. But even so, his integrity demanded that he give the scoundrel at least one sturdy biff in the jaw. After that, he could afford to feel generous and enlightened and drag the man by the scruff of his neck to the nearest mental institution.