THERE AND GONE. ONE MOMENT. JUST ONE moment and already his purple jacket is not even a spot in the distance. I’m running through murky green water with a cop on my back shouting for me to stop, but I’m too frantic. Too startled, too afraid to even register that I might be breaking the law. Still, it’s Sammy—my Sammy, my little brother. And this is all my fault.

He could die and it’d be all my fault.

The crowd thins as I keep running and I know I’m past the point of no return. Passageways toward different train lines pop out at me and I try to pretend I’m Sammy. Think like him, get inside his mind.

Sammy has Asperger’s, a form of autism that can make social interactions about the worst thing in the world for him.

It’s why he hates crowds, people touching him, why he only drinks from a red water bottle, and communicates difficult-to-process emotions through random facts. He favors things on the right side, so I take every right turn. He hates noise, so I take the routes that are the most silent.

“Stop right there, miss! Stop!” The cop keeps screaming, but I barely have time to register him. The water surges up my calf, but I don’t stop. I have to find Sammy. I need to find him. Still—I need to lose this cop first.

Sammy likes small spaces, so I know that finding him won’t be easy. Luckily, it’s also the perfect way to go where this cop won’t follow. I veer away from a passageway leading toward a shuttle and move toward the tracks of the F train.

I can almost feel the officer’s shock pulsing through the air as I do the unthinkable.

I run hard until I’ve gathered enough momentum to leap off of the ground and onto the subway tracks. Water splashes around me and I pray to whoever is listening that the electricity has been shut off because of the storm.

“Are you insane?” I hear him scream behind me. His voice breaks, its booming authority turning into something fearful and frantic.

Good, don’t follow me. And not just because I know he’ll try to take me back, but because the only person who should be doing something as reckless as jumping down to train tracks to save Sammy is me.

Then there’s a second splash of water and a bright white flashlight shoots on. He’s followed me—that stupid cop is following me.

“Get back here, miss! You’re going to get yourself killed.” His voice returns to an authoritative shout. He sounds almost unfeeling, his tone completely free of any trace of the previous fear. He doesn’t even sound sympathetic, as if the fact that my little brother is off somewhere in this dark and flooded underground tunnel is something he doesn’t care about. Something he won’t even pretend to care about.

I feel anger boiling in my blood, rising with each water-soaked step I take, propelling me deeper and deeper into the tunnel. The water is only an inch or two past my ankles, but it’s rising steadily as rainwater continues to leak from the concrete ceiling. My heart is still seizing in my chest when I finally see it—just the type of exit Sammy would take, if I’m right and he’s jumped on the tracks. A slightly open door, just shorter than my five-foot-three frame, appears on the right, and no matter how convoluted this all is, I know I’ve made the right choice. Sammy thinks like this—complicated and in tangents: every right turn, the small enclosed track tunnels, the tiny door on the right side in the tiny enclosed tunnel.

This has to work. I have to be right.

I fake a left turn just swiftly enough to make the cop think I’m about to turn, but then I leap for the door and almost smile as I hear the cop fumble in my wake.

I must be the only one who was an all-star on the JV girls basketball team in middle school.

I try not to get too cocky as I press toward the door, my fingers latching onto the handle, and I’m suddenly jerked back by a hand on my raincoat.

I don’t think. My body is a roll of nerves and energy that can’t possibly be contained, even by some disgruntled cop.

So I don’t hesitate; I don’t think about future consequences or anything as practical as that. I just do.

All at once my limbs explode and I kick him hard in the stomach. My arms follow suit, and I push at his shoulders until he loses his balance.

With a grunt, he stumbles back into the water on the tracks and I keep moving, thoughts of Sammy, alone and shivering somewhere, clouding my mind.

I’m coming, Sams. Don’t worry I’m coming.

I yank open the door and find a long, twisting staircase. I pull up the flashlight app on my iPhone and begin my descent. The farther down I go, the more my thoughts spiral. The cop lying in the water, the storm raging around us, Sammy lost to me forever.

He’d once told me that I was like a rock in the middle of an ocean. It was a rare moment of self-reflection that had made me hug him hard until he yelped and pushed me away from him. He didn’t have to explain what he meant—I already knew. The world for Sammy was like a shifting current. Things moved too fast for him and too slow all at once. He could never find the right momentum or ever catch a break, but I was his rock. I stayed solid for him and immobile even when things got tough.

But I’d been too busy thinking of Ezra and our breakup to notice how agitated he’d been. I’d failed as his big sister, as his rock in the middle of a torrential sea.

And that blooming thought of failure pulses through me as I reach the bottom of the staircase and see nothing there. A storage room, just an empty storage room with metal shelves filled with nothing.

Still, I ransack the room until the metal shelves dig into my skin and leave scratches. I call his name and the only voice that echoes in my ears is my own. I run up the stairs, through the darkness and out the door, running my shaking hands through my hair. My thoughts shift to the cop. Maybe he can help. Maybe if he sees how shaken, how close to breaking apart I am. Or maybe if I beg, beg until my voice goes hoarse and I run out of words.

But the cop isn’t there. I pushed him—kicked him—into the water and he hasn’t gotten up. He hasn’t chased after me. Suddenly, a different panic takes hold of me.

I just hit a cop. And possibly knocked him unconscious. What is that . . . like thirty years in prison? I’m screwed. I’m so unbelievably screwed.

And what if he’s injured, what if he’s dead— drowned in the dark water? What if he has a wife and kids? People who depend on him, love him, and need him? What if I’ve just ruined all their lives just to find Sammy?

I search through the water, which has gotten much deeper since I ran through that door. My eyes strain in the white light of my phone, searching for movement. I almost frantically jump in myself when a hand claps me hard on the shoulder.

I freeze before turning to look at the angry police officer.