“You should hear Mike talk about Ben’s first kung fu lesson,” Christina replied with equal mirth.

“You know,” Ben said, passing them both, “you two are starting to annoy me.”

“I’m sorry,” Christina said. She looked at Jones. “This is really rude of us.” And then they both burst out laughing.

“I should cancel their bonuses,” Ben muttered as he left the office. If they ever got bonuses.

“I can’t believe this,” Baxter said, shifting from one edge of the passenger seat to the other. “Sheila Knight never did anything wrong in her life. Except maybe talk to you.”

“Nonetheless,” Mike insisted, hands on the steering wheel, “she’s lying. Or at the very least, holding something back.”

“She told you everything you wanted to know.”

“Or seemed to. Trust me on this, Baxter. She’s lying.”

“And you know this because…”

“I just know.”

“Of course. So why don’t you drag her downtown and give her a lie-detector test?”

“Because there would be no point.” Tulsa traffic was not normally an issue, but there were a few exceptions, and Seventy-first on Friday afternoon was one of them. Even after the street had been widened to the size of something you’d expect to see in Dallas, it still clogged, worse and worse the closer you got to the on-ramp for Highway 169. Maybe it was employees fleeing en masse from the chain stores and restaurants that seemed to have sprung up overnight on this boulevard. “She’s not a suspect. I don’t know that she’s a material witness. I can’t force her.”

“She might comply anyway.”

“She might. But the test wouldn’t be admissible in court. And frankly, I think polygraphs are unreliable and easily manipulated.”

“Easily manipulated?” Baxter waved a hand across her brow. “Is this the sphincter dodge?”

“That works, actually.” It was well-known in police circles that tightening the sphincter muscle during the control questions could send the polygraph a false signal, thus disguising subsequent lies. There were several ways, actually. Putting a tack in your shoe and stepping on it at the right time. Anything that elevated the subject’s blood pressure could throw off the machine. “But it isn’t the easiest way.”

“And what is the easiest way, O Great and Powerful Superior Officer?”

“Just lie on the control questions. The test administrator asks control questions, then pertinent questions, then compares the two and looks for a change in the readout. If you lie on the control questions, though, then lie on the rest, there will never be any observable change.”

“Fine. If we can’t use the polygraph, how do we prove she’s lying?”

“We don’t have to. I already know.”

“Because…”

“Did you see her eyes?”

“Yes. Brown. Large.”

“Did you notice the crinkling lines? When she smiled?”

“I don’t recall that she ever smiled.”

“She did. When she talked about how much she used to enjoy going over to the Faulkner home.”

“Okay. And you saw crinkling lines?”

“Right here.” Mike pointed to the corner of his eye. “An authentic smile engages the whole face, including the crinkling lines, in a generally relaxed expression. A lying smile doesn’t. When it doesn’t come naturally-when it’s being put on for show-the mouth may change, but the face doesn’t.”

“So you’re saying there were no crinkling lines.”

“There were, actually, but they were more crow’s-feet than laugh lines. It wasn’t authentic.”

“If you say so.”

“I do. And there’s more. Just before she smiled, there was a flash of-I don’t know. Didn’t last for even a second. She wiped it away and manufactured the fake smile. But for a fleeting instant before that, there was… something else.”

“Which was?”

“Hard to be certain. A frown, a scowl. A grimace. The textbooks call them microexpressions, and they’re hard to spot. But that was her true, natural reaction. And that tells me there’s something Sheila Knight didn’t give us. That perhaps her visits to the Faulkner home weren’t all as wonderful as she suggested.”

“Are you serious about this? I can’t wait to read your report. ‘Suspect had suspicious crinkly lines.’ “

“Don’t laugh, Baxter. Knowing who is and isn’t telling you the truth is critical to being an effective homicide investigator.”

“Clearly. I’m surprised they don’t teach this at the academy. Crinkly Lines 101.”

Mike blew air through his teeth. “Look, if you’re going to make fun-”

“Perish the thought.” She swallowed her smile. “I’m surprised you didn’t come down harder on Dr. Bennett. Now she seemed nervous to me.”

“Some people are. Especially when the police come calling. That doesn’t mean they’re lying.”

“And she never made eye contact when she was answering your questions.”

“Who does?” Mike downshifted and moved into the right-hand lane, hoping to find an escape route from the traffic. “Most people are uncomfortable with extended direct eye contact. Looking away is simply deferential. If you see someone who’s killing himself to maintain eye contact, he’s either trying to sell you something or lying. Or both.”

Baxter laughed. “I did notice Sheila kept doing that thing with her hair. Touching it. Brushing it back.”

“True. But don’t confuse personal tics with lying. Everybody has a few nervous habits-biting nails, twirling pencils. It’s not the same thing. What you look for are discrepancies-differences between what the person is saying and what the person is doing. Saying yes but subtly shaking the head. That sort of thing.”

“Speaking of personal tics,” Baxter said, “what was all that nonsense about-what was it? Hyperthermal luminous paraffin?”

Mike grinned. “I was just giving her something to worry about.”

“So now you think Sheila Knight killed Erin?”

“I don’t think anyone killed Erin except Erin. That’s your delusion, not mine.” He paused, hung a hard right. “Even if there was a murder, it couldn’t have been Sheila Knight. She has an airtight alibi.”

“She might’ve had an accomplice.”

“And in that unlikely event,” Mike said, “she will now be desperate to get to her accomplice and inform him that his hands are coated with hyperthermal luminous paraffin.”

“And she won’t call, because you fed her all that BS about being able to trace and eavesdrop on her phone conversations.” Her head tilted to one side. “Not bad, Morelli. Will Blackwell authorize a stakeout team?”

“For this case? Not a chance. But I called for an unmarked car to watch her office. For her own safety, you know,” he said, winking. “That’ll get us to sundown. Ben’s investigator might take over after that. Mind you-just because Sheila’s lying doesn’t make her a killer. But if she is working with someone else-we’ll find them.”

Baxter nodded grudgingly. “It hurts to admit it, but-not bad detective work, Sherlock. You should teach a course.”

“I do. Every year. You’d know that if you’d gone to school on the right end of the turnpike.”

Baxter gave him a long look. “I never figured you for a teacher. How’d you get started on that?”

“There was an opening at the academy, and frankly, I needed the scratch. Alimony payments were killing me. But I found I enjoyed it. It’s a kick, really. Hanging out with the baby cops and wannabes.”

“That must require patience. Some of those new recruits are pretty green.”

Mike grinned. “Not as green as I was, way back when.”

“Oh yeah?”

“Oh yeah. Bright-eyed and bushy-brained, that was me. I thought the world was my private crime lab. Thought I could do no wrong.”

“Did that change?”

Mike gave her a wry expression. “Yeah. That changed. All too soon.” He hung a left and glided onto the highway. “Sorry. Didn’t mean to get all boring and autobiographical on you.”

“Not at all. It wasn’t-I didn’t-” Her hand stretched out, but almost immediately she drew it back. “I’m not complaining. Hey-this is the first time we’ve talked for more than ten minutes without yelling at each other or threatening bodily harm.”