He leaps onto the running board and grabs the side-view mirror with one arm, pounding on the window with his other hand just as the engine roars to life and the truck surges forward, spewing sand.

Nick sees Vasquez appear at the tightly closed passenger window at the moment the truck shatters the main door with a fearsome jolt. It hurtles ahead toward the heart of the enormous tent-the operating and recovery rooms. Suddenly, Sarah appears, locked between the headlights. Nick barely has time to register that she is there, to see the terror in her eyes, before the grille of the truck hits her at the base of her ribs, tearing her nearly in half. Nick sees blood gush from her mouth as she flies backward toward the ORs.

Vasquez is slammed against a support pole and driven off the running board. The truck bursts into the brightly lit space, scattering victims and hammering into patients. Zmarai hits the brakes, hurling Nick to the ground like a rag doll. Paralyzed by Sarah’s gruesome death, Nick stares unseeingly at the floor. He knows the truck is going to explode and that he’s about to die. The image filling his mind is Sarah. Suddenly, there is a blur of movement from his right side. Heavy arms wrap around his shoulders and drive him backward into the base of a massive refrigeration unit filled with blood and blood products.

Umberto!

Glass shattering, the refrigerator topples onto Nick and his friend, covering them both. Nick is semiconscious, facedown under the glass-and-steel appliance. Units of blood are torn open and their contents pour onto his head and torso. Then, amidst the chaos and screaming, Zmarai’s ancient truck explodes. The roar is deafening. Blast-furnace heat floods Nick’s face and arms.

Then there is nothing.

It is more than twenty-four hours before Nick begins to regain consciousness. His skin is badly scorched, his ears are ringing, and his hearing is muffled, but he can still hear the surgeon telling him that rather than leave the tent, Umberto had rushed back to Nick’s side and saved his life. He is told that Umberto is still in a coma and there is only one other survivor, an orderly, who is still touch and go. There are twenty-eight fatalities. Some of the bodies, including Sarah Berman’s, have not been pieced together yet.…

“Jeez Marie, Nick,” Junie cried. “I just looked over at you and you weren’t there. It’s like the RV is on automatic pilot.”

“I was here,” Nick lied, flexing his shoulders and back against the chilly perspiration that was soaking into his clothes.

The rain had become a downpour, and the RV was blasting through it into the darkening night.

“You want to go home?”

“I said I was okay,” Nick snapped.

Junie knew better than to react. Whatever had been going on was leaving him, and no one had gotten hurt. The episodes had been coming fewer and farther between. He’d be okay.

“On the highway, this here bus is like a battleship against a bunch of rowboats,” she said.

“I… know. I’m sorry.”

He slowed the RV to forty.

“You’re going to be okay, Nick,” the nurse said in what was half statement and half query. “You’re going to be fine.”

Nick’s reply was a grim smile.

“Come on, gang. It’s a simple question. An atom that loses one or more electrons becomes a what?”

Franz Koller bristled at the students’ lack of respect for their education, and thought of killing them-every one of them. An aerosol blast of sarin, the nerve gas used in the Tokyo subway attacks, would do just fine. The glorious image brought a smile-twenty-two perfect teenage bodies, simultaneously tumbling from their chairs, writhing in seizure, soiling themselves as respiratory failure set in. His grin broke the tension between him and the tenth-grade chemistry class at Woodrow Wilson High in Coltin, California. The kids saw him brighten, and a few actually smiled back. Again, he pictured them squirming on the floor, their tiny backs arched in agony, mouths agape like fish on a dock, madly sucking for breaths that just wouldn’t come. The visual made him laugh out loud. The students joined in and laughed with him.

“Oh, pleeeeasseee,” Koller begged, kneeling in mock desperation on the scuffed linoleum floor. “Please take pity on your poor old substitute teacher and answer the question. I know we subs aren’t supposed to actually teach, but I really know chemistry, and I’m determined to impart some of my knowledge to you.”

Though he was born and raised in Austria, his speech was free of any accent-unless, of course, he wanted one to be there. On bended knee, praying before his class for some bright star to respond, Koller clasped his hands together and bowed his head. He paused for added dramatic effect before looking up and raising one eyebrow as if to add “pretty please, with sugar on top.” It was a phrase he sometimes used when begging his victims to hold on just a little longer.

The class giggled, though somewhat cautiously. Little by little, he was winning them over. Koller was incredibly skilled at that-winning people over-especially those he was in the process of studying for what he called a non-kill-murder that appeared not to be murder at all.

He laughed with the class as he rose, but his laughter was not at what they were finding funny. He was continuing the fantasy about their mass destruction-specifically the vision of their parents, cocooned in white chemical suits, coming to identify their bodies.

“One of you must know the answer. An atom that loses one or more electrons becomes?”

The only sound was the ticking of the wall-mounted clock. No wonder America’s world dominance was on the decline, Koller mused. For years, in between contracts, he had protected his identity as a killer by creating new identities as a substitute teacher. He enjoyed the deception and the teenage girls, but until recently he also enjoyed making complex concepts clear. He had well-supported teaching credentials in California and Florida, where he also had residences. At last, a tiny hand, third desk from the back, tentatively came up. The killer’s eyes flashed with delight. All heads turned toward the back to see who it was.

“Ah! Ms. Rebecca Woodorf.”

The girl looked puzzled at his remembering her name. After all, what substitute teacher, without the aid of a seating chart, who had heard their names only once during attendance, could pull off such a feat?

“Please stand up, Rebecca. Stand up. It appears you are our only salvation. Now, prove to me and to your fellow classmates that America’s tenth graders can stay with the Russians, Chinese, and Japanese when it comes to inorganic chemistry.”

Koller rubbed his hands in anticipation. It was a game he enjoyed playing during the sometimes interminable periods between contracts-to win over the class so that he was all they would be talking about after school. He actually had never finished college, dropping out after he was recruited by a psychology professor to meet with the people who would eventually teach him how to kill for money. They were the ones who would supply him with unassailable teaching credentials. He was a quick study in every area. And while there was much to learn, he had a head start, because when it came to manipulating others and controlling their behavior, he already had a Ph.D. with high honors.

Rebecca rose. Her black sweater was tight against her slender frame, accentuating her burgeoning womanhood in a most appealing way. Koller noticed, too, that her lips were tight across her teeth. She was shy, though not too shy to show pride in her body. Interesting.

“Mr. Greene?” Rebecca said in a small voice.

“Yes. Go ahead. Give it to us.”

“May I go to the bathroom?”

The classroom exploded in laugher. Rebecca glanced about, mortified. Koller kept his expression stern and his arms folded tightly across his chest. The laughter subsided.