***I pick up towards the end of the original Chapter 50***

TRIS

"I didn't come here to steal anything, David."

I twist and lunge toward the device. The gun goes off and pain races through my body. I don't even know where the bullet hits me. Only that it does.

I can still hear Caleb repeating the code for Matthew. With a quaking hand I type in the numbers on the keypad.

The gun goes off again.

CALEB

The moment that Tris disappears around the corner, a great weight lifts from my chest, only to almost immediately be replaced by another kind of ache. A deep chilling feeling similar to the one I used to have any time I would hide my books in my Abnegation bedroom and then later scold my wayward sister for whatever small failing I can find. It's guilt and this time more powerful than any other. It freezes me in place even as I'm aware of chaos occurring all around me and that I should seek more secure shelter.

There is a war inside me between my Erudite mind and Abnegation heart. My sister. She has just willingly gone to die for me. My father's voice surfaces in my memory, teaching both of us about sacrifice and the Abnegation way. I know she has done this out of love. And that the reason is because I was not. I see my parent's faces before me and wonder what they would say of their son. What their faces would look like. Filled with sadness? Love? Forgiveness?

I take a deep breath and look around the corner at the bodies Tris has left in her wake. The path is clear. I know what I have to do. What I want to do.

TRIS

There are black edges on my vision, but I can't tell whether from lingering effects of the Death Serum or because I am about to pass out from blood loss. It does not matter. I hear Caleb's voice speaking again. The green button.

So much pain.

I start to fall, and slam my hand into the keypad on my way down. A light turns on behind the green button.

I hear a beep, and a churning sound.

I slide to the floor. I feel something warm spread beneath me. I reach for it. Red. Blood is a strange color. Dark.

CALEB

I slow as I make the final turn, logic leading to caution. There is no point is making this decision and dying before I can enact it. One guard stands before the smoking hole that Reggie's explosives have left of the doors to the Weapons Lab. His caution tells me everything I need to know. The Death Serum is likely still active inside.

Something catches my eye off to the right. It is the backpack that Tris carried this far, with the explosives and other supplies. Including the protection suit. A gun lies nearby, next to a guard with a single bullet between the eyes. I grab it. I have studied the human anatomy. My memory tells me the most vulnerable point and the amount of force it will require at the back of the guard's neck.

I sneak forward; his eyes are still fixed on the scene before him. Through a curling haze I can see the bodies of two additional guards collapsed in the room beyond. They were not Divergent. They could not defeat the Death Serum. It is definitely still active.

Once I have made the decision, it is relatively easy. I am tall enough to bring the proper angle and force. The guard crumples before me. As I knew he would. I grab the backpack and pull out the suit, slipping it over my clothes in seconds just as I had practiced. The hooded mask obscures my vision and the gloved hands make it difficult to grip the gun.

I advance forward, my body quaking as I step through the Death Serum, knowing I will not survive. Just ahead I see her, blood seeping into clothes from two bullet wounds. I see David, and I know I was right to follow.

David's gun is trained on Tris even as she works at the keyboard. I bring up the gun before me even as the first sensation of heaviness hits me. The Death Serum. I will not survive.

But Tris can.

I breathe in. Out. Aim. Just as Tobias taught me. And I smile a little, thinking that he will be relieved knowing his teaching was remembered at the crucial moment. I squeeze the trigger, my eyes never leaving the center of David's chest.

The Death Serum has begun to work inside me now. I can feel its effects spreading throughout my entire body. I stumble forward, wanting to see, to make sure that I haven't been too late. I dimly see Tris, her hand hitting the green button. The tension leaves my chest even as my eyes grow heavy and my thoughts jumbled.

I didn't fail.

TRIS

From the corner of my eye, I see David slumped over in his chair.

And my brother, in the suit I left in the backpack, stumbling into the room between us.

"Caleb?" I whisper in a cracked voice, fear enclosing itself around my heart. The Death Serum must be working its way through his system. His eyes, behind the plastic mask, already seem glassy. But he is still breathing.

"You've-" Caleb's voice is weak, but clear, "sacrificed enough." He exhales, and I watch his eyes close and I know that my brother is dead. But I refuse to focus on the grief that threatens to crush me. I push that aside. A great weight lifts from my shoulders because I know my brother, who hid his true nature from me throughout our childhood, made a new choice in faction. The Abnegation way of our parents. And his last words tell me that it wasn't out of grief. But out of love. For me.

I look again at David and notice the blood blooming across his clothing. Now I see the bullet hole must be buried somewhere in his shoulder. His arm hangs down limply just above where he dropped the gun he used to shoot me.

I shift my weight and push with my good arm against the floor to bring me to my feet. Pain blossoms from my left side knocking me back to the floor. I hear more running feet from outside the Weapons Lab and reach for the gun that dropped with Caleb.