``Right,'' said the fingerprint man. ``Also, if you're going to believe those prints, you'll have to look for a killer who's a top-grade piano player.''

He demonstrated by playing an imaginary piano, doing a staccato passage with a broadly exaggerated attack. To make it clearer he shifted to acting out, but with no change of manner, the killing of Rose Mallory. His hands snatched at an imaginary bucket, swooping down hard to grab it and coming away with equal snap like a ball that's been bounced hard. In the same way he pantomimed grasping a mantel and bouncing cleanly off that, pressing his hands against the floor and bouncing cleanly off that. He was moving like a ballet dancer, playing for laughs. If Rose Mallory's killer acted this way, catching up with him was going to be a cinch. We'd know him by his stretch pants and the flowers he'd wear twined in his hair.

Perhaps if Felix had first come upon us when this boy was not cavorting so gaily up and down the hall outside the murdered woman's apartment, we might have had less trouble convincing Felix of our seriousness. This, you will remember, was still New Year's Day. By the time Felix turned up it was early afternoon, which, one would think, would be late enough so that by then, except for small children and a few hardy souls who had not yet sobered up, it could have been expected that people would no longer be having any sort of active interest in the previous night's noisemakers and paper hats.