My Sister's Grave (Tracy Crosswhite, #1)(42)

The students in the front of the classroom flinched and leaned back when the spark shot a crackling white bolt across the gap between the two spheres. Tracy cranked the handle of the electrostatic generator, increasing the speed of the two rotating metal discs that caused the bolt to continue firing. “Lightning, ladies and gentlemen, is one of nature’s most dramatic illustrations of the energy form scientists like James Wimshurst and Benjamin Franklin sought to harness,” she said.

“Wasn’t he the dude who flew the kite in a storm?”

Tracy smiled. “Yes, Steven, he is the dude who flew the kite in a storm. What he and those other ‘dudes’ were trying to determine was whether energy could be converted into electricity. Can someone point to hard evidence that they succeeded?”

“The lightbulb,” Nicole said.

Tracy released the handle. The spark died. Her freshmen sat in pairs at tables equipped with a sink, Bunsen burner, and microscope each. Tracy turned on a water faucet at a front table. “It helps if you think of electricity as a fluid capable of flowing through objects. When an electric current flows we call that what, Enrique?”

“A current,” he said, generating laughs.

“I meant, when an electric current can flow through a substance we call that substance . . . ?”

“A conductor.”

“Can you provide me with an example of a conductor, Enrique?”

“People.”

The students again laughed.

“No joke,” Enrique said. “My uncle was working a construction job in the rain, and he cut through an electrical line and nearly killed himself, except another guy yanked him off the saw.”

Tracy paced the front of the room. “All right, let’s discuss that scenario. When Enrique’s uncle cut through the electrical line, what happened to the flow of electricity?”

“It flowed into his body,” Enrique said.

“Which would be evidence the human body is, in fact, a conductor. But if that is the case, why didn’t the coworker get shocked when he touched Enrique’s uncle?”

When no student responded, Tracy reached below her desk and retrieved a nine-volt battery and a lightbulb in a bulb holder. Two lengths of copper wire extended from the battery, and a third wire extended from the bulb holder. The opposite ends were alligator clips. Tracy attached the alligator clips to a piece of rubber tubing. “Why didn’t the bulb light?”

No one answered.

“What if the worker who touched Enrique’s uncle was wearing rubber gloves? What could we conclude?”

“Rubber isn’t a conductor,” Enrique said.

“That’s right, rubber is not a conductor. So the power from the battery will not flow through the rubber tubing.” Tracy attached the clips to a large nail. The bulb lit. “Nails,” Tracy said, “are made up mostly of iron. So what can we conclude about iron?”

“Conductor,” the class said in unison.

The bell rang. Tracy raised her voice over the obnoxious clang and the scraping of barstool legs on linoleum. “Your homework is on the board. We will continue our discussion of electricity on Wednesday.”

Back at her desk, Tracy began to put away the demonstration, preparing for her next period. The volume of noise from the hallways increased, which meant someone had opened the door to her classroom. “If you have questions, please see me during my regular office hours; you’ll find them posted on my door along with a sign-up sheet.”

“This won’t take long.”

Tracy turned toward the voice. “I’m preparing for a class.”

Roy Calloway let the door shut behind him. “You want to tell me what it is you think you’re doing?”

“I just did.”

Calloway approached her table. “Questioning the integrity of a witness who had the courage to come forward and do his civic duty?”

Hagen had called Calloway, which Tracy had thought likely when he’d shut the door in her face that Saturday. “I didn’t question his integrity. Did he tell you I questioned his integrity?”

“You did everything but call him a liar.” Calloway leaned his palms flat on her table. “You want to tell me what you think you’re trying to accomplish?”

“I just asked him the news program he was watching.”

“That is not your place, Tracy. The trial is over. The time for asking questions is done.”

“Not all the questions got asked.”

“Not all the questions needed to be asked.”

“Or answered?”

Calloway pointed a finger at her, the way he used to when she was young. “Leave it alone. Okay? Let it be. I know you also drove to Silver Springs and have been talking to bartenders.”

“Why didn’t you, Roy? Why didn’t you check to make sure House wasn’t telling the truth?”

“I didn’t need to check to know he was lying.”

“How, Roy? How did you know?”

“Fifteen years of police work, that’s how. So we’re clear, I don’t want to hear about you ordering any more transcripts or harassing witnesses. I do, and I’ll have a talk with Jerry and tell him how one of his teachers isn’t committed to teaching, that she’d rather play junior detective. Do you understand?”