1 I leaned into the turn, bike tires humming until the pavement roughened and my smooth ride dissolved into a rumble, unheard but felt as Nine Inch Nails blared in my earbuds. The mirror attached to the handlebar was less than helpful with the vibrations, but traffic had stopped and I slowed, feeling the afternoon heat from the street as I scanned the commuter cars, their windows up and air-conditioning on. My spandex kit emblazoned with a nonexistent bike-messenger service gave me some slack, but I''d had enough near misses with doors to be wary. That''s why the helmet and skidproof gloves. Both had the sweepers'' triangle logo on them, as did my backpack and water bottle strapped to the bike frame. So did the blueprint tube over my shoulder, the metal tube heavily stickered with grunge and alternative rock bands. Reason one for a bike, I thought as I rolled past the cars. Here outside the university campus, the low, squat buildings did little to hide the late sun, and I squinted as I found the intersection.

The light changed before I got there, and after making eye contact with the driver on my left, I jammed on the pedals in time with the hard beat in my ears to cross the street. I kept up with traffic, muscles moving smoothly as I watched the street and sidewalk in a familiar pattern of defense. My gaze, though, kept returning to a glinting shimmer half a block up. It looked like a heat mirage and I stifled a call of warning when a woman stepped right into the hazy glow and picked it up like dog doo. Immediately she tripped on the sidewalk-and the distortion of dross clinging to her heel was gone, used up in a flash of bad luck. Two doors away, a more certain gleam lurked under a painter''s scaffold. The shimmer was unseen by nearly the entire world''s population, oblivious as they walked through it to snag wisps of dross and carry them over the entire city. A tiny half percent had some sense that it was there, and an even smaller fraction, like me, could actually do something about it.

The city of St. Unoc just east of Tucson had one of the highest percentages of magic users this side of the Mississippi, bringing the usual ratio of one in a thousand to more like eight out of ten. The ratio at our closed campus, named after the small city, was even higher. But that was what made St. Unoc University special-and my job essential to keeping the silence of our existence. I signaled a lane shift, checking behind me before sliding over to give the hazy glimmer a wide berth. Dross never broke on me, but it might pop my tire if I drove through it. No reason to tempt fate, I thought, knowing someone would be along to sweep it up.

It was a rather large chunk of dross, though. A mage was being careless with his or her magic. Big surprise, I thought as I bunny-hopped up onto the curb, slowing to a crawl as I swung a leg over the saddle and rode on one pedal to the bike rack before a three-story office building. Behind me in the street, a horn blared followed by a crunch of fender. I turned, knowing the accident would be right where that heat-distortion-like haze was. Or had been, I thought as the drivers in ties and power dresses lurched out of their vehicles, tired and surly from the heat. Maybe I should have tried to gather it up, but I had a pickup, and even the best of us wouldn''t sweep dross during rush hour. Besides, the haze of latent energy was gone, used up in the crash.

Any left was probably stuck under one of the cars, where it would stay, slowly breaking down as snapped belts and leaking hoses: a long-running total. The bike rack by the door was a small pocket of stillness between the ornamental cacti and the overgrown lavender, and I jerked one earbud out, letting it hang as I took off my helmet and fluffed my bangs to ease my helmet-head coif. Sometimes it sucked to be able to see the origins of the bad luck that was so common that it was accepted as the natural order of things and not someone else''s magical waste. "Reason two for a bike," I whispered, my blueprint tube and backpack over my shoulder as I timed the revolving door and went inside. "Door-side parking is always available." I pulled my other earbud out as the cool of the building hit me. There was a definite flow of people leaving, and I got only a cursory check at the front desk as I signed in and opened my bag for inspection. The elevator was empty, and Reznor fought with the Carpenters on the way to the top floor.

The air felt different when I got out. Clearly I was among the point-five percent. Magic. I could smell it more than the unspent jet fuel from the nearby air base: the tang at the back of my throat and a hint of ozone pricking my nose. Which isn''t always a good thing, I thought when the floor receptionist recognized the sweeper insignia on my kit and pointed me down a hall even as she reached for a phone to alert the building manager. Most mages could see the waste they generated when doing magic: a flicker of distortion, a hazy glow near the eye''s blind spot. The two required semesters of dross manipulation and capture were usually enough to give magic users the skills to direct dross into traps without touching it, but only Spinners and sweepers had the ability to physically touch dross without it breaking on them in a wash of bad luck. Which was how I landed my sweeper job eight years ago at the soul-crushing age of eighteen.

Eighteen and pigeonholed into a low-status but surprisingly high-demand job, for even though I couldn''t do magic, my dross-handling skills made me not only an essential worker but also a frontline defense against deadly shadow. Most people, though, only saw a trashman, and as I strode down the hall I heard a whispered "That''s Petra Grady? She looks like a bum." My stilted smile faltered. Bum? Sure, I looked like a messenger, but they''d called me because they couldn''t handle it. Besides, if I had shown up wearing velour robes and carrying three yard-long engraved sticks, I''d end up in an insane asylum. "Petra Grady? Ms. Grady?" The man''s voice pulled me to a stop and I turned on my heel. A heavy man in a suit a half size too small for him was making his arm-swinging way to me.

"Guilty as accused," I said, hating my high voice, but five-foot-four, small, athletic frames seldom make for a low, sexy lilt. "Thank you for coming on such short notice." The man, clearly the building''s manager, strode forward, pulling me into his wake as we continued down the corridor. It went without saying that he was a mage. "Um, I''m Mark," he added. "The psi manager." Which meant he was the one where the buck stopped when there was a dross issue. He''d whispered the last, but that he said it meant the entire floor was probably mages.

Psi manager wouldn''t be on his pay stub, but I''d agree he was a manager of some sort as I took in his lunch-spotted tie, ample middle, and scuffed brown shoes. He looked like a mundane, but I was willing to bet that the ornate class ring pinching his plump finger was actually his lodestone. The piece of glass at the center had been utterly unremarkable until he had bonded to it, allowing him to use and store the light energy that touched it-or at least half of the light energy. Mages used the wave half; Spinners used the particle. What was left after separating light into its two parts was discarded as dross. That was where I came in; for though I couldn''t do magic, I could touch the waste they made with impunity. Still, seeing the stone on his finger, a long-dead envy flickered and went out. "I, ah, found out about the spill this morning," Mark added, clearly nervous.

"But I think it''s been free-roaming for two days." He pointed to the left and we went deeper into the building. "That''s two days too long," I said, and he shrugged. You leave dross alone and it gets bigger, attracting other dross until its natural dissociation isn''t spilled coffee and crashed computers but six-car pileups and elevators dropping to basement floors. "And a right here," he said as we turned into a short hall ending in double fire doors. "It''s in a back office. Aren''t you supposed to have a spotter?" he added as he ran his badge at the reader. The speaker beeped, but the door didn''t move.

Flushing, Mark tried again. "My assistant is graduating this week," I said as he tried a third time-and got the same result. St. Unoc''s university made a practice of pairing promising new students with experienced sweepers for a yearlong work-study/assessment program. I, though, had been working with the same mage for the last two years as she gathered data for her thesis on dross abnormalities. But Ashley''s thesis was written and she''d be gone next week. I was going to miss her. I hadn''t thought I''d like a housemate when she first proposed sharing rent, but Ashley had been surprisingly accommodating.

For a mage. "It does this all the time," Mark said, nervous as he ran his card again, and finally the lock disengaged. "It''s not the escaped dross." "Sure," I said, preferring to reserve judgment. Mark shoved through the doors and held them for me. I followed, soaking in the feel of the large, close-ceilinged, open-concept room, with its low partitions and full-spectrum lights. It was after hours and the desks were empty. Hazy dross drifts lingered like dust bunnies under chairs and in the corners, evidence of their hidden magic: covert coffee-reheats, avoid-the-boss glamours, forget charms to steal from the fridge and hide illicit computer use.

It was small stuff that when left to its own devices did little more than cause a p.