Alongside the laptop lay a scaled color printout of a human skull, with curved arrows indicating a region on the top of the skull that looked like a jigsaw puzzle. There were measurements written in McClure’s hand at the blunt end of the arrows, while their sharper ends pointed to the area of impact that had resulted in the death of Martel Gale.

“Regulation baseball bat is forty-two inches,” Kevin said. He sat on the guest side of Walt’s office desk, facing his uncle on the other side of the open screen.

“Okay.”

“I’m doing this two ways—with and without a choked grip. Come on around.”

Walt came around the desk and leaned in behind Kevin, his left hand on the boy’s shoulder. The screen showed two animated figures, looking like mannequins against a plain background. Several boxes spread around the screen outside the center window held software tools, including one that contained two other, much smaller mannequin-like figures.

“On the right is your victim,” Kevin said. “All six-foot-four and a half of him. A frickin’ giant. On the left is the giant killer. The bat is to scale and I Googled the average arm length for specific heights. You gave me five-foot-four, so this guy on the left is five-foot-four. So check it out.”

He set the screen into motion. The figure on the left—not “a guy,” but Kira Tulivich, in Walt’s mind—hoisted the baseball bat and, in frame-by-frame slow motion, brought it down onto Gale’s head. Kevin used the mouse to draw an arrow at the area of impact and then pointed to the printout to his left.

“Not even close,” Walt said.

“He’s too short,” Kevin said, referring to the Kira figure. “This guy was hit way up on top of his head. Even if I set it so he doesn’t choke up,” he said, adjusting the bat in Kira’s hands and animating the action for a second time, “the bat hits the skull in about the same place, the problem being this guy just isn’t tall enough to reach the top of the victim’s head. So what I did was put him up a single step. Seven inches. Because maybe the guy with the bat’s standing on a step when he connects with this guy.” He repositioned the smaller figure. “And though it’s better, it’s actually too high, too tall. I mean if the victim is at the perfect distance away . . . sure. It can be made to work this way . . .” He moved Gale forward and this time, when animated, the bat landed squarely on the top of Gale’s head. Walt shuddered, able to see beyond the world of computer-realized mannequins. “But if it isn’t absolutely the perfect distance, what happens is a length of the bat connects from the back of the skull to the front, making like a trench instead of a pit.”

“So, no good,” Walt said.

“It takes a perfect storm,” Kevin said. “That’s all I’m saying. A step height and the perfect separation between the two. My guess, you could run this a dozen times and you’d be lucky for it to come out right once or twice. It’s not a high-percentage shot.”

“And the high-percentage shot?”

“That’s different. Two options.” Kevin replaced the Kira figure with another, taller figure from the toolbox. “Six foot. Six-foot-one. Wouldn’t matter if it was two-handed or one. The length of the guy’s arms more than compensates. Slightly choked-up on the bat . . .” He completed setting up the scene and put the new figure into motion. The bat was lifted high in the air and came down squarely with the end of the bat impacting the top of Gale’s skull—exactly as McClure had suggested. “That’s a frickin’ bull’s-eye.”

“Six foot. Six-foot-one,” Walt said, his voice giving away his relief.

Kevin looked over his shoulder and into Walt’s face. “What’s up with that?” He didn’t wait for an answer. “I didn’t say it was the only option, did I?” When Kevin got behind a computer he became arrogant. Walt considered reprimanding him but didn’t want to get into it with him. “Here’s the thing I forgot: tiptoes. When you really whale on a bat—” He scooted out, stood up, and demonstrated, rising to his tiptoes as he swung high overhead. “Okay?” Slipping back into the chair, he manipulated the laptop to replace the taller assailant with a slightly smaller one. The figure rose up onto bent feet and the bat came down, the impact perfectly reflecting Mc-Clure’s notes. Kevin highlighted some areas and made the assailant stand once again.

Walt returned to his earlier thought: there were only two people living on the Engleton property. A minute earlier Kevin had all but ruled out Kira. “How tall?” Walt choked out.

Kevin moved the cursor arrow to the top of the head of the assailant figure, and steadied it there. A yellow box popped up alongside the arrow containing the measurement: 172.7 cm.

“Inches?” Walt asked dryly. He already knew the answer—his height when wearing a pair of boots.

Kevin asked the software for the conversion. A new number filled the box: 68 in.

“Five-foot-eight,” Kevin said. “Or more precisely, five-foot-eight on tiptoe—six foot, six-foot-one.”

Walt remembered kissing her. Coming slightly off his heels to reach her lips.

Walt shut his office door and returned to his chair and stared at the e-mail there waiting to be sent, his request for the fingerprint work. It wasn’t a matter of thinking clearly. He couldn’t think at all. The number, five-foot-eight, stuck in his head like a wedge, like a baseball bat to the top of his skull. Back to Kevin’s perfect storm: a smaller person elevated on a step at just the right distance from Gale; a taller person killing the man easily. But it was the last option that wouldn’t leave his thoughts, the last option that had been building like a tsunami inside him.

He hit Enter and the computer made a swishing sound indicating the e-mail had been sent.

“Some cases don’t get solved,” she’d said to him. “Some cases go cold.”

At the time, he’d thought she’d been protecting Kira.