"I think I need to rest," Leo mutters, right before his eyes roll back in his head and he pitches off the chair. Darius, who has been pacing in the hallway, rushes into the room and crouches anxiously over Leo.

Cara takes his pulse. "He'll be okay, she reassures Darius. "Help me turn him over for a second." She takes a syringe out of the first aid kit, yanks Leo's boxers down, and gives him a shot.

"It will fight off infection," she says primly to Darius, who shrugs and checks the surveillance screens before heading back to sentry duty. Cara does take a good look at Leo before she covers him back up. Maybe not so prim after all. We make eye contact and it's my turn to smirk and raise an eyebrow at her. She shrugs her shoulders, smiling sheepishly.

"Now," Cara says, stepping over Leo and wiping her hands on her jeans, "tell me what you've observed and give me your hypothesis. I can tell you have one."

I lead her over to the computer and pull up the data files. "This is not like the simulations we ran in Dauntless," I explain, slipping into instructor mode. "For those, the computer code was linked with transmitters in the serum. The simplest programs just stimulated the amygdala, but for the final test, the program was more complicated. We would take the data generated from the initial fear responses and program them into a fear landscape – a mental obstacle course of all your worst nightmares."

"So your success is judged by how well you master your fears?" Cara asks.

"No, not really," I respond. "Your success is judged by how well you master yourself. I'm not sure anyone really overcomes fears," I muse, "except perhaps with the passage of time."

"And that just probably brings new fears."

That's certainly been my experience, I think. In my last trip through my fear landscape, there were some changes, and they were not necessarily for the better. I start, as I realize something…

"What is it?" Cara asks, leaning eagerly toward me.

"Nothing really…"

"Tell me."

"It's just… My fears that are about conditions, they haven't changed much." She looks confused. "I will always be afraid of heights," I wave my hand dismissively. "But my fears about people, about me in relation to people – those change."

"I doubt that's relevant," I add, shrugging.

"I bet it is," she counters. "We see patterns and make connections, even when we don't consciously realize it, you know. Did Tris have many fears?"

"No – only seven. I only know of one person with fewer in recent Dauntless history. And, as you know, simulations don't work on Divergent – we usually know we're in one and can break out. Tris generally defeated the simulations in 2 to 3 minutes or less. That's unheard of."

Christina starts laughing. She turns and grins at us, pointing up at the screen. "I'm totally hilarious!" she shouts over the headphones.

I look up, startled to see Tris and Christina in brightly colored dresses and lipstick, riding in a truck with Marcus. I feel my eyes narrowing.

Christina rolls her eyes, "Oh, relax. Marcus, or 'Destroyer of Lives,' as I just called him, is on some kind of mission with us to Amity."

Cara snaps her fingers at me. "Focus, Four."

I give my head a little shake and turn back to the computer, starting the recorded simulation where I left it, moving past the sleep time. There's another shot of Tris getting out of bed and dressed. I try not to stare at her image, especially when she strips down to shower.

Pointing to the brain scans, I say "I know we usually stimulate the amygdala for fear landscapes, but that doesn't seem to be the focus of activity for this simulation – it's this region," I sweep my hand over the front part of the image.

"That's the prefrontal cortex," Cara says promptly.

"And sometimes here," I point at the "Tobias" section of her brain.

Cara squints at the screen. "Orbitofrontal cortex."

"OK, and that means what?"

"In a nutshell, those are the command and reward centers of your brain."

On the computer screen, I see Tris has returned to my room, where Christina is waiting for her, holding the blue glass statue. I make a guttural huff of surprise and lunge for the controls.

"Watch, watch," I say excitedly. "I think there might be something about that statue!" I replay the scene, and sure enough, as soon as we see the statue in Christina's hands, the activity line spikes and the prefrontal cortex flares. It's over so fast, as soon as Christina puts the statue down, that you'd miss it if you didn't know where to look.

"What does it mean?" I ask Cara.

"I don't know. Yet. What do you think it means?"

"I think she's fighting the simulation," I answer.

"Does anything else seem to make her prefrontal cortex light up?"

"Pretty much when anyone is making a decision – anyone, not just Tris."

"And the orbitofrontal?" she asks, before I can even finish my last sentence.

I hesitate. "When she's with me," I mumble.

"How, with you?" Cara presses.

I sigh. "When she's touching me or kissing me, when we're being affectionate. Well…" I flush. Cara gestures impatiently. One time when we were…intimate…both areas illuminated."

"So what's your hypothesis, Four?" Cara says softly.

I am reluctant to tell her what I'm thinking, as though just the act of saying it out loud will make it true.

"Jeanine said that Tris is doing this to herself," I start, slowly. "I don't think this is a fear landscape at all - there's no code, no programming. I think this is a self-generating simulation, controlled by those other parts of her brain. Tris is creating the story, and she just self-corrects any inconsistencies that might suggest it's a simulation."

Cara nods, her eyes distant, as she thinks it through.