"Holy shit," I say, as I start to read Linus's note.

"Dear Cara, Tobias, Beatrice, Fernando, et al., if you are reading this, then I am likely dead or otherwise unavailable to you. I regret that is the case, for my sake, of course, but also for yours. I have been waiting decades for you, for a group of people with the will and the abilities to put the situation in our city to rights. It is such a shame that it took so long and had to get so bad before this could happen, but I give you my love, my hopes, and even better, my notes.

I have spent a lifetime, more than 60 years, collecting all the information I could about this city, the people in it, and the nature of our experiment. You will not be able to read it all, but the stronger Divergent among you should spend a day or two connected to this database through the purple serum. While you may not consciously remember everything, you may find you remember the information when you need it - that is how the Divergent brain works. It is very good at cataloguing random pieces of information, picking out what's important and connecting it together. It is very good at reacting to external stimuli and extreme situations in an orderly way. Divergent really should be called the Convergent, because they are inherent community, idea, and order builders. They are not particularly good at dealing with the mundane and necessary, however, so the genetic diversity is still important for a successful society in peacetime.

Speaking of that, did you ever wonder why our city is so empty? This was once a place called Chicago, and more than two million people lived here, even more outside the wall. We are now only about 2,500 people. That is very much on purpose; isolating a genetic trait within a small population will cause it to propagate more quickly. The problem is that our population is too small, especially with the recent killings. I believe our original population was quite genetically diverse, with the exception of a tendency toward Divergence, but now, about 100 years into the experiment, the inbreeding is starting to propagate bad mutations, too. So, it is not just the fact that our sponsors appear to have disappeared that is driving the urgency of your mission to open to the rest of the world: we are collapsing from within.

The other thing you need to know is that I believe at least one person from outside the experiment lives among us. I do not know who it is; I only know that I saw evidence in the perimeter a little over a decade ago that someone had recently entered. I also see evidence in the computer system of a ghost in the machine - someone who is manipulating the network, and I do not believe it was Jeanine or any Erudite working for her. Be very careful; Fernando has strict orders not to connect your safe house computers to the network. There is no question we are being monitored, and they will not be able to use off-network computers that way. And as you will see in my notes, be careful about Amity. I have long suspected but never been able to confirm the Faction has closely guarded, secret information about the perimeter.

As I write this, a deep sense of unease is overtaking me, and I have learned to trust such hunches. I fear that I must bring this to a close and get the chip to one of you. One last thought for my dearest Cara," I can see that the note does, indeed, end here. "I love you and hope I have helped to keep you safe - you and Will were, without a doubt, my proudest achievement."

I look at Cara in surprise. What could that last sentence mean?

"Don't look at me like that," she sniffs, wiping her hand across her eyes. "He was my grandfather."

"What?" I sputter. "He was what?"

"My grandfather," she says more calmly.

I wheel around on Fernando. "Did you know that?"

Fernando nods. "Yeah. In fact, I don't understand how little you Dauntless all seem to know about each other. I mean, the total population of Erudite is only about 500. I don't know everybody, and of course there are transfers every year, but in 30 years of living there, I at least feel like I recognize everybody."

"Yeah, and you found out the hard way you didn't really know them as well as you thought you did, didn't you?" I say, crossing my arms.

Fernando sighs. "That's fair, I guess, and I certainly had secrets of my own. And I forget you started in Abnegation. It's the smallest faction, which might be part of the reason it breeds so many Divergent, but your peeps don't socialize much, do they? But Dauntless? Come on! There are bars, paintball games, only one dining hall..."

"I've only been there for two years," I mutter. "Anyway, once Max and then Eric both were leaders, things got dangerous; it was just a good idea to keep your head down. And, well, I'm kind of a private person to begin with."

"We noticed," Cara deadpanned.

"Fine, maybe everyone does know everyone else and that's part of the problem. I have no idea. But I think it's my turn to take the purple serum and look around."

Cara nods and holds up a syringe. "I figured you would feel that way. I just need to patch you in and inject you."

I frown as I watch her attach the electrodes to my head and the heart monitor to my chest. "How does this work, anyway?" I ask.

"Well," Cara says, swabbing my arm, "the simple version? Your brain uses both electrical impulses and chemical reactions to process information and create activity. This serum is basically a hybrid: it replaces some of your normal brain chemistry and reroutes the electrical impulses. Linus thought Jeanine had no idea that the electrical pathways could go in both directions."

"I'm not going to get stuck in there like Tris did, am I?" I ask nervously, feeling woozy as the drug starts to take effect.

"You'll be fine, Four. Tris actually had code embedded in the chemical compound. It started Tris on the scenario, and then let her take it over; they used small electric shocks to keep her in the same simulation - they just didn't know that she was making some excursions of her own. You will remember you're in a simulation of sorts the whole time, and we also can insert messages, if we need to. In a worse case, we can kill the electrical signals."

"You mean, I basically only had to unplug Tris to save her?"

"Yep."

With that, I feel as though I'm spinning down a drainpipe, with pulses of light flashing at me.

After what seems like days, I bring myself back up out of the files. Yawning, I pull the electrodes off my forehead and look around. Cara is still there, working on one of the computers, and Fernando is lying on a cot across the room. At first, I think he might be hooked into the computer, but then I hear him snoring. Figures.

"Oh, you're out!" Cara says. "Excellent. Fernando just came out about 30 minutes ago. Be forewarned that while it's more restful than running away from an ambush through the marsh, it's not actual sleep. Your brain didn't get much rest, so you should probably take a nap."

I shake my head. "Too much to do," I say, yawning again. "Did Inez come back yet?"

"Yes," Cara says softly.

"Did they find Jose?"

"They did. He's alive. Barely. He was left for dead, and I'm not sure he will ever regain consciousness."

I press my lips together grimly.

"Okay, I'm going to go look in on them, but let's get a few of the others hooked up in here."

"Sure. But first, what do you remember?" she asks.

"Oh, well," I pause. "I'm not sure how to answer that question, actually. Except that the perimeter is mined with neurotoxins and electrified, with a fence that stretches for thousands of miles. There is a monitoring station, and Linus and whoever he was working with at the time figured out how to neutralize the perimeter, at least temporarily." I tap my forehead. "I've got that part where I can see it."

"Interesting," Cara says, regarding me clinically. "If I'm not mistaken, you have very good, conscious recall, but only of what you went in wanting to know. That's good - you know, sometimes the simplest answer is the right one. We didn't even think of that, but I bet it'll work for the others, too."

I yawn again. "Okay," I can't even keep my eyes open. "Good. Well, you were right. I'm going to have to take a nap." I stretch out on a cot and feel myself sinking again, this time into a comfortable blackness.