Dark Rivers of the Heart

another, studying the pane as he'd studied the frame.
        Nothing.
        "Magnetic powder," Davis said. "That's the ticket."
        Wertz flicked on the fluorescent lights. He went to a supply cabinet and returned with a jar of magnetic powder and a magnetic applicator called a Magna-Brush, which Roy had seen used before.
        Streamers of black powder flowed in rays from the applicator and stuck where there were traces of grease or oil, but loose grains were drawn back by the magnetized brush. The advantage of the magnetized over other fingerprint powders was that it did not leave the suspect surface coated with excess material.
        Wertz covered every inch of the frame and pane. No prints.
        "Okay, all right, fine, so be it!" Davis exclaimed, rubbing his long-fingered hands together, bobbing his head, happily rising to the challenge.
        "Shoot, we're not stumped yet. Damned if we are! This is what makes the job fun."
        "If it's easy, it's for assholes," IVertz said with a grin, obviously repeating one of their favorite aphorisms.
        "Exactly!" Davis said. "Right you are, young master Wertz. And we are not just any assholes."
        The challenge seemed to have made them dangerous Roy looked pointedly at his wristwatch.
        While Wertz put away the Magna-Brush and jar of powder, David Davis pulled on a pair of latex gloves and carefully transferred the window to an adjoining room that was smaller than the main lab. He stood it in a metal sink and snatched one of two plastic laboratory wash bottles that stood on the counter, with which he washed down the lacquered frame and glass. "Methanol solution of rhodamine 6G," Davis explained, as though Roy would know what that was or as if he might even keep it in his refrigerator at home.
        Wertz came in just then and said, "I used to know a Rhodamine, lived in apartment 6G, just across the hall."
        "This smell like her?" Davis asked.
        "She was more pungent," Wertz said, and he laughed with Davis.
        Nerd humor. Roy found it tedious, not funny. He supposed he should be relieved about that.
        Trading the first wash bottle for the second, David Davis said,
        "Straight methanol. Washes away excess rhodamine."
        "Rhodamine always went to excess, and you couldn't wash her away for weeks," said Wertz, and they laughed again.
        Sometimes Roy hated his job.
        Wertz powered up a water-cooled argon ion laser generator that stood along one wall. He fiddled with the controls.
        Davis carried the window to the laser-examination table.
        Satisfied that the machine was ready, Wertz distributed laser goggles.
        Davis switched off the fluorescents. The only light was the pale wedge that came through the door from the adjoining lab.
        Putting on his goggles, Roy crowded close to the table with the two technicians.
        Davis switched on the laser. As the eerie beam of light played across the bottom of the window frame, a print appeared almost at once, limed in rhodamine: strange, luminescent whorls.
        "There's the sonofabitch!" Davis said.
        "Could be anybody's print," Roy said. "We'll see."
        Wertz said, "That one looks like a thumb."
        The light moved on. More prints magically glowed around the handle and the latch hasp in the center of the bottom member of the frame.
        A cluster: some partial, some smeared, some whole and clear.
        "If I was a betting man," Davis said, "I'd wager a bundle that the window had been cleaned recently, wiped with a cloth, which gives us a pristine field. I'd bet all these prints belong to the same person, were laid down at the same time, by your man last night. They were harder to detect than usual because there wasn't much oil on his fingers."
        "Yeah, that's right, he'd just been walking in the rain," Wertz said excitedly.
        Davis said, "And maybe he dried his hands on something when he entered the house."
        "There aren't any oil glands in the underside of the hand," Wertz felt obliged to tell Roy. "Fingertips get oily from touching the face, the hair, other parts of the body. Human beings seem to be incessantly touching themselves."
        "Hey, now," Davis said in a mock-stern voice, "none of that here, young master Wertz."
        They both laughed.
        The goggles pinched the bridge of Roy's nose. They were giving him a