Jacob stares at the paper. “You had me at hello,” he says.

I hated Mark Maguire before I even laid eyes on him. Jess had changed-instead of focusing only on me when we had our sessions, she’d answer her cell phone or fire back a text message, and every time she did, she smiled. I assumed that I was the reason for her distraction. After all, everyone else seemed to get sick of me quick enough when we were in the middle of a conversation, and it was bound to happen with Jess, although that was my greatest fear. Then one day she said she wanted to tell me a secret. “I think I’m in love,” she said, and I swear to you, my heart stopped beating for a second.

“Me, too,” I burst out.

CASE STUDY 1: Let me stop here for a minute and just talk about prairie voles. They are part of only a tiny fraction of the animal kingdom that practice monogamy. They mate for twenty-four hours, and then, just like that, they’re together for life. However, the montane vole-which is a close relative, sharing 99 percent of the prairie vole’s genetic makeup-has no interest in anything except a wham-bam-thank-you-ma’am one-night stand. How come? When prairie voles have sexual intercourse, the hormones oxytocin and vasopressin flood the brain. If the hormones are blocked, prairie voles behave more like those slutty montane voles. Even more interesting, if prairie voles get injections of those hormones but then are prevented from having sex, they still become slavishly devoted to their would-be mates. In other words: you can make a prairie vole fall in love.

The opposite, though, isn’t true. You can’t give a shot of hormones to a montane vole and make it lovesick. It just doesn’t have the right receptors in the brain. It does, however, get a flood of dopamine to the brain when it mates, the hormonal equivalent of Man, that feels good. It’s just missing the other two hormones, the ones that help pinpoint that ecstasy to a particular individual. Sure enough, if you genetically modify mice, removing the genes that affect oxytocin or vasopressin, they can’t recognize mice they’ve already met.

I am a prairie vole, trapped in the body of a montane vole. If I think I’ve fallen in love, it’s because I’ve considered it analytically. (Heart palpitations? Check. Lack of stress in her company? Check.) And it seems to me to be the most likely explanation for what I feel, although I could not truly tell you the difference between feelings for a romantic interest versus feelings for a close friend. Or in my case, my only friend.

Which is why, when Jess told me she was in love, I reciprocated.

Her eyes widened, and so did her smile. “Oh my God, Jacob,” she said. “We’ll have to double-date!”

That was when I realized we weren’t talking about the same thing.

“I know you like having time alone for our sessions, but it’s good for you to meet people, and Mark really, truly wants to get to know you. He’s a part-time ski instructor over at Stowe, and he thought maybe he could give you a free lesson.”

“I don’t think I’d be very good at skiing.” One of the hallmarks of Asperger’s is that we can barely walk and chew gum at the same time. I am forever tripping over my feet or stumbling on a curb; I could easily see myself falling off a chairlift or snowballing down a mountain.

“I’ll be there to help, too,” Jess promised.

And so, the following Sunday, Jess drove me to Stowe and got me fitted for rental skis and boots and a helmet. We hobbled outside and waited near the ski school sign until a black blur whizzed down the hill and sprayed us in a tsunami of powdered snow. “Hey, babe,” Mark said, pulling off his helmet so that he could grab Jess and kiss her.

In one glance I could tell that Mark Maguire was everything I was not:

1. Coordinated

2. Attractive (if you’re a girl, I mean)

3. Popular

4. Muscular

5. Confident

I could also tell that I was one thing Mark Maguire was not:

1. Smart

“Mark, this is my friend Jacob.”

He leaned down into my face and yelled, “Hey, dude, cool to meet you!”

I yelled back, “I’m not deaf!”

He grinned at Jess. He had perfect, white teeth. “You’re right. He is funny.”

Had Jess told him I was funny? Had she meant that I made her laugh because I told good jokes or because I was a joke?

In that instant I hated Mark Maguire viscerally, because he’d made me doubt Jess, and up until then I had known, unequivocally, that we were friends.

“So what do you say we give the bunny hill a try?” Mark asked, and he held out a pole so that he could drag me to the rope tow. “Like this,” he said, showing me how to grab on to the moving rope, and I thought I had it right but my left hand got screwed up with my right and I wound up spinning backward and collapsing on the little kid behind me. The guy running the rope tow had to shut it off while Mark hauled me to my feet again. “You okay, Jacob?” Jess asked, but Mark brushed her off.

“He’s doing great,” Mark said. “Relax, Jake. I teach retarded kids all the time.”

“Jacob is autistic,” Jess corrected, and I turned around so fast that I forgot about the skis and fell down in a heap again. “I’m not retarded,” I shouted, but that statement is somewhat less resonant when one cannot even untangle one’s own legs.

I will say this for Mark Maguire: he taught me how to snowplow efficiently enough to make it down the bunny hill twice, solo. Then he asked Jess if she wanted to take a run up the big hill while I practiced. They left me in the company of seven-year-olds in pink snowsuits.

CASE STUDY 2: In laboratory studies, scientists have learned that, when it comes to love, a very tiny portion of the brain is actually involved. For example, friendship lights up receptors all over the cerebral cortex, but this isn’t true with love, which activates parts of the brain more commonly associated with emotional responses like fear and anger. The brain of a person in love will show activity in the amygdala, which is associated with gut feelings, and in the nucleus accumbens, an area associated with rewarding stimuli that tends to be active in drug abusers. Or, to recap: the brain of a person in love doesn’t look like the brain of someone overcome by deep emotion. It looks like the brain of a person who’s been snorting coke.

That day at Stowe, I did two runs with the help of a kid who was learning to snowboard, then inched myself toward the main ski lift. I leaned against a rack where people could store their skis while they were in the lodge getting hot chocolate and chicken nuggets, and I waited for Jess to come back to me.

Mark Maguire is wearing a suit. He has dark circles under his eyes and I almost feel bad for him, because he must be missing Jess, too, until I remember how he hurt her.

“Can you state your name for the record?” the prosecutor asks.

“Mark Maguire.”

“Where do you live, Mr. Maguire?”

“Forty-four Green Street in Burlington.”

“How old are you?”

“I’m twenty-five,” he says.

“And what do you do for a living?”

“I’m a grad student at UVM and a part-time ski instructor at Stowe.”

“How did you know Jess Ogilvy, Mr. Maguire?”

“She’d been my girlfriend for five months.”

“Where were you on Sunday, January tenth, 2010?” Helen Sharp asks.

“At Mama’s Pizza in Townsend. Jess had a tutoring session with Jacob Hunt, and I liked to come along every now and then.”

That is not true. He just didn’t like that she was spending time with me and wouldn’t give me up for him.

“So you know Jacob?”

“Yes.”

“Do you see him in the courtroom today?”

I stare down at the table so I can’t feel the serrated edges of Mark’s eyes. “He’s sitting over there.”