7. They sweat through the pads of their feet.

8. Scientists have found that dogs can smell the presence of autism in kids.

You’re making that up, she said.

No. Really.

How come you don’t have a dog?

There were so many answers to that question, I didn’t really know where to begin. My mother, for one, who said that anyone who could not remember to brush his teeth twice daily did not have the fortitude to take care of another living creature. My brother, who was allergic to nearly anything with hair on it. The fact that dogs, which had been my passion after dinosaurs but before crime scene analysis, had fallen out of favor.

The truth is that I would probably never want a dog. Dogs are like the kids in school I cannot stand: the ones who hang around and then leave when they realize they are not getting what they want or need from the conversation. They travel in packs. They lick you and you think it’s because they like you, but it’s really just because your fingers still smell like your turkey sandwich.

On the other hand, I think cats have Asperger’s.

Like me, they’re very smart.

And like me, sometimes they simply need to be left alone.

Once I leave Mark Maguire to steep in his own conscience for a few minutes, I grab a cup of coffee in the break room and check my voice mail. I have three new messages. The first is from my ex, reminding me that tomorrow is Open School Night for Sasha-an event that, by the looks of things, I’m going to have to miss yet again. The second is from my dentist, confirming an appointment. And the third is from Emma Hunt.

“Emma,” I say, returning her call. “What can I do for you?”

“I… I saw that you found Jess.” Her voice is husky, full of tears.

“Yes. I’m sorry. I know you were close to her.”

There are sobs on the other end of the line.

“Are you okay?” I ask. “Do you need me to call someone for you?”

“She was wrapped in a quilt,” Emma chokes out.

Sometimes, when you do what I do for work, it gets easy to forget that, after you close the file on a case, there are people who suffer with the fallout for the rest of their lives. They’ll remember one little detail about the victim: a single shoe lying in the middle of the road, a hand still clutching a Bible, or-in this case-the juxtaposition between being tenderly tucked into a quilt and being murdered. But there’s nothing I can do for Jess Ogilvy now except bring the person who killed her to justice.

“That quilt,” Emma sobs, “belongs to my son.”

I freeze in the act of stirring cream into my coffee. “Jacob?”

“I don’t know… I don’t understand what that means…”

“Emma, listen. It might not mean anything at all, and if it does, Jacob will have an explanation.”

“What do I do?” she cries.

“Nothing,” I tell her. “Let me. Can you bring him down here?”

“He’s in school-”

“Then after school,” I say. “And, Emma? Relax. We’ll get to the bottom of this.”

As soon as I hang up, I take my full mug of coffee and empty it in the sink; that’s how distracted I am. Jacob Hunt admitted to being at the house. He had a backpack full of Jess Ogilvy’s clothes. He was the last person known to see her alive.

Jacob may have Asperger’s syndrome, but that doesn’t preclude his being a murderer.

I think of Mark Maguire’s flat-out denials about hurting his girlfriend, his unscarred hands, his crying. Then I think of Jacob Hunt, who cleaned up Jess’s house when it looked like it had been vandalized. Had he left out the intrinsic detail that he was the one who’d wrecked it?

On the one hand, I have a boyfriend who’s a jackass but who’s grief-stricken. I have his boot prints outside a cut screen.

On the other hand, I have a kid who’s obsessed with crime scene analysis. A kid who doesn’t like Mark Maguire. A kid who’d know how to take a murder and make it look like Mark Maguire did it and then attempted to cover his tracks.

I have a kid who’s been known to hang out at crime scenes in the past.

I have a homicide, and I have a blanket that links Jacob Hunt to it.

The division between an observer and a participant is nearly invisible; you can cross it before you even know you’ve stepped over the line.

On the way home from school, I am gripping the steering wheel so hard that my hands are shaking. I keep looking in the rearview mirror at Jacob. He looks like he did this morning-wearing a faded green T-shirt, his seat belt snugly fastened over his chest, his dark hair falling into his eyes. He is not stimming or withdrawn or exhibiting any of the other hallmarks of behavior that flag the fact something is upsetting him. Does that mean he didn’t have anything to do with Jess’s death? Or he did, and it simply doesn’t affect him the way it would affect someone else?

Theo has been talking about math-a problem he did that no one else in the class understood. I am not absorbing a single word. “Jacob and I have to swing by the police station,” I say, training my voice to be as level as possible. “So Theo, I’m just going to drop you off at home first.”

“What for?” Jacob asks. “Did he get back the results on the backpack?”

“He didn’t say.”

Theo looks at me. “Mom? Is something going on?”

For a moment I want to laugh: I have one child who cannot read me at all, and another who reads me too well. I don’t answer but pull up to our mailbox instead. “Theo, hop out and get the mail, and you can let yourself into the house. I’ll be back as soon as I can.” I leave him standing in the middle of the road and drive off with Jacob.

But instead of heading to the police station, I stop off at a strip mall and park. “Are we getting a snack?” Jacob asks. “Because I’m actually quite hungry.”

“Maybe later.” I get out of the driver’s seat and sit beside him in the back of the car. “I have something to tell you. Some very bad news.”

“Like when Grandpa died.”

“Yes, a lot like that. You know how Jess has been gone for a while, so you couldn’t have your meeting on Sunday? The police found her body. She’s dead.” I watch him carefully as I speak, ready to mark a flicker of his eye or a twitch of his hand that I might read as a clue. But Jacob, completely impassive, just looks at the headrest in front of him.

“Okay,” he says after a moment.

“Do you have any questions?”

Jacob nods. “Can we get a snack now?”

I look at my son, and I see a monster. I’m just not sure if that’s his real face or if it’s a mask made of Asperger’s.

Honestly, I’m not even sure it matters.

By the time I reach the police station with Jacob, my nerves are strung as tight as the strings on a violin. I feel like a traitor, bringing my own son to Detective Matson, but is there an alternative? A girl is already dead. I couldn’t live with myself, with this secret, if I didn’t acknowledge Jacob’s involvement.

Before I can even ask for him to be paged by dispatch, the detective walks into the station lobby. “Jacob,” he says, and then he turns to me. “Emma. Thanks for bringing him in.”

I don’t have any words left to say. Instead, I look away.

Just like Jacob.

The detective puts a hand on my shoulder. “I know this isn’t easy… but you did the right thing.”

“Then why doesn’t it feel that way?” I murmur.

“Trust me,” Matson says, and because I want to-because I need someone else to take the wheel for just a moment while I struggle to breathe-I nod.

He turns back to Jacob. “The reason I asked your mom to bring you here,” Matson says, “is because I want to talk to you. I could really use your help with some cases.”

My jaw drops open. That is a blatant lie.