“Only if you can tell me what an atom that loses one or more electrons becomes,” Koller said, matter-of-factly.

There was an audible gasp and Rebecca’s lips tensed even more. The students stared from their classmate to their substitute teacher and back, trying to get a read on each of them. Behind his deep brown contacts, Koller gave them nothing to fix on. In the next teaching gig, the lenses would be green or navy, covering his true eye color, a startlingly pale blue. His store-bought mustache would be on or off depending on his mood. Koller took pride in disguising not only his thoughts, intentions, and facial features, but his physique as well, which for this job, thanks to skillfully applied padding and latex, looked doughy and poorly maintained-anything but capable of snapping a human neck with the quick grip and twist of one hand.

“Are you serious?” Rebecca managed.

“The bathroom key in exchange for an atom that loses one or more electrons.”

Koller paused just the right amount of time before breaking.

“Nah,” he said with a broadening grin and a dismissive wave of his hand. “I’m just messin’ with you. Of course you can go.”

That did it. The students applauded and howled even louder this time, and Rebecca, who moments before had looked as if she were going to be sick, laughed along with them. Clearly still uncertain and off balance, she walked warily to the front of the class, past the substitute they knew as Mr. Robert Greene. Cautiously, she took the key attached to a model of a chlorine atom off his desk, and moved to the door. Once there, she paused before exiting the room, and turned back.

“Mr. Greene?”

“Yes, Rebecca?”

“A cation,” she said simply.

Koller, though not the least surprised, gave her a playful bow and applauded, encouraging her classmates to do the same. She beamed then turned to go, the backs of her thighs taunting Koller as she closed the door behind her.

Playing head games with fifteen-year-olds. Ogling a child’s ass. This day was becoming truly torturous.

In the past, teaching high school chemistry had been reasonably diverting, in addition to providing him with an effective cover. It was not a good idea to be a single man, leading a secret life, without having some sort of socially acceptable profession. In addition, he had never done that well with too much downtime between contracts. But now, the queens of vapidity, YouTube, the Internet, and television, had taken their toll, and in most of the so-called students there was little mind remaining to mess with.

This was the end of the teaching, he vowed. From now on, when he needed a diversion, he would just drive out to the woods and kill something. It had been two weeks since the last contract. How long would he be made to wait?

He recalled with fondness the nurse from Charlotte, whom he had studied and then manipulated to ingest a lethal overdose of sleeping pills, complete with a handwritten suicide note.

Nicely done.

You call, Franz Koller delivers. The CSI goofs would have given up searching for clues in the nurse’s death before the first commercial. Koller heard the growing restlessness behind him and knew he was ignoring the class. Screw them. They were lucky he didn’t go out to the local poison gas store for some sarin.

Sleepers and a suicide note. The woman was a magnificent non-kill-more intense than screwing a hundred Rebecca Woodorfs would have been. Belle Coates, first in her class at nursing school, fluent in three languages, was so exquisitely sexy, lying there naked, helpless, and utterly outmaneuvered, slipping away in the lukewarm water of her bathtub. Just watching her breathing slow and her head slip beneath the surface had given him a fearsome erection. He never even had to touch her. Sex was all about control, and how much more control could there be than-

The classroom door opened and closed.

Rebecca Woodorf returned from the bathroom, less shy and more confident.

“You have some TP stuck on your shoe,” Koller said casually as she passed.

The girl reddened, quickly glanced behind to see, then stared in confusion at her teacher.

“Just kidding,” Koller said. “Gotcha.”

This time, the laughter from her classmates was directed at her. Koller did nothing to stifle it. The girl’s shoulders sank under the humiliation as she scuffled back to her desk.

Fun, fun, fun ’til her daddy takes the T-bird away, Koller sang to himself.

He sent a portly boy named Sommers to pass out a quiz left for them by their teacher. They were all quiet now, busily scribbling in their booklets, answering questions a sixth-grader should have known.

Ten minutes more… ten min-

His cell phone began ringing. The tone was AC/DC’s famous guitar riff from “Back in Black.” The students recognized the song immediately and looked up at Koller with surprise and reverence. Mr. Robert Greene was hip-the coolest chemistry teacher around.

Their delight did not come close to Koller’s.

“Who is it, Greene?” one of the class toughs called out. “One of your biker babes?”

“I wouldn’t be caught dead on a motorcycle, Harcourt,” Koller said, flashing back to the contract on a surgeon from Chicago who rode his gleaming Harley into oblivion.

The bolts supporting the front and rear calipers, carefully modified by the master of the non-kill, disconnected simultaneously at the top of a long 10 percent grade on the interstate. Under the best of circumstances, investigators would probably never have spotted the modification. In the case of Lewis Leonard, M.D., a tractor-trailer saw to it that there was no modification left to detect.

Nicely done.

“So what’s the call all about?” Harcourt asked far too loudly.

“It’s nothing,” Koller said, bursting to tell the truth to the arrogant little shits, but knowing he wouldn’t. “Just an alert that an art dealer I like to buy things from has posted an item for bid on eBay. I get notified whenever he lists something new.”

“What are you buying, a blow-up?”

“Ever hear of sarin, Stankowsky?”

“What?”

“Nothing.”

“What is it, then? What are you buying?”

Koller glanced up at the clock. Four minutes before last bell.

“Want to see?” he asked.

Anything but chemistry.

The class begged him in unison.

He clicked a link in his e-mail and opened up an eBay product description and photo. Then he passed his cell phone around, allowing each student a chance to see the wooden desk lamp shaped like an old sailing ship that was now open for bids starting at $0.99.

“That’s a piece of crap,” one student exclaimed. “Wal-Mart wouldn’t carry it.”

There were guffaws from some of the others, but Koller didn’t react.

“What do you think, Rebecca?” he asked.

Rebecca’s eyes were fixed on her test booklet.

“I don’t know,” she mumbled.

“Take a look,” Koller said. “You’re the smartest one in this class-the only one whose opinion I would trust. The only one worth saving when the flood comes. I think it’s simply beautiful. How about you?”

Rebecca glanced up at the phone as if half expecting something gross.

“It’s a very nice lamp,” she managed.

What it is, Koller was thinking, is a job for Mr. Greene-buckets of money for work he would happily do for free.

Last bell sounded, and Koller was out the door without even looking back at his class.

As soon as he was back at his apartment, he would decode the message encrypted within the picture of the lamp. Then, once he had all the facts, he would decide if $990,000 was enough for the job or whether $1,500,000-a million five-would be more appropriate.

Later that day, John Sykes, the principal of Woodrow Wilson High, called to say that the feedback from his chemistry classes was excellent, especially F block, the last period. Could Greene possibly come in and substitute again tomorrow?