The man dies three feet away from me.

I don't scream. Don't run. Don't do anything except stand there, invisible, while his blood pools toward my shoes.

I hadn't meant to stop. The alley was a shortcut home from the FBI field office, nothing more. I'd walked it a hundred times. But tonight I heard sounds, a scuffle, a grunt, the wet noise of a blade finding flesh, and my feet stopped moving before my brain caught up.

Behavioral instinct. The curse of training your mind to analyze violence instead of flee from it.

The victim crumples. Mid-forties, professional clothes, expensive watch. His eyes are still open, staring at the wall behind me like he's looking for answers in the brick.

The killer straightens. Methodical movements. He wipes the blade on the dead man's coat, two strokes, precise. No wasted motion. Everything about him screams practice.

My fear spikes, and the edges of me dissolve.

I know what's happening. I've known since I was eight years old and my father's fist swung toward my face and the world went silent because suddenly, impossibly, he couldn't see me.

I'm vanishing.

The light bends around me, or I bend around it, I've never understood the physics of it. But my hands fade, then my arms, then all of me dissolves into the darkness between shadows.

The killer goes still.

His head tilts. Like a dog catching a scent.

"Interesting," he says to the empty air.

My fingers go numb. He can't see me. I know he can't see me. But something in his posture suggests awareness. Recognition.

He takes a step toward where I'm standing.

"I know you're there." His voice is calm. Cultured. Wrong. "I can feel you. Your fear is... exquisite."

I don't breathe. Don't move.

He takes another step. Two feet away now. If he reaches out,

"You're special," he says. "I've been looking for someone special."

A siren wails in the distance. His head turns toward the sound, and in that moment of distraction, I run.

My feet make no sound on the pavement. I'm not even sure they're touching the ground. The invisibility holds, fueled by terror, and I don't stop until I'm three blocks away, pressed against a dumpster in another alley, gulping air that tastes like rust and garbage.

When I finally force myself to check, my hands are visible again. Shaking, but solid.

I close my eyes.

The image of the dying man sears itself behind my eyelids. His blood. The killer's calm, practiced movements. The way he'd spoken to nothing like he knew exactly what I was.

I've been looking for someone special.

In thirty years, I've never met anyone who could sense me when I vanished. No one. Not my father, not the foster families, not the colleagues I've kept at calculated distance.

But this killer knew.

He felt me.

And now he's looking for me.

I press my palms against the brick wall and count backward from fifty until the shaking stops. Then I pull out my phone and watch the screen glow in the dark.

I should call 911. Report what I saw. But what would I say? I was invisible in the alley when a man was murdered? They'd either laugh or commit me.

I could go home. Pretend it didn't happen. Let someone else find the body. Let the investigation proceed without my impossible testimony.

That's what I've always done. Fade. Disappear. Let the world move on without me.

But the victim's eyes won't leave my mind. Staring at the wall like he was asking me to remember his face.

I pull up the number for the FBI tip line and press call.

"I need to report a murder," I say when they answer. "An alley off K Street. Behind the parking garage."

"Can I get your name, ma'am?"

I hesitate. Then: "Anonymous."

"Can you describe what you saw?"

I describe it. Everything except my presence. I was passing by, heard sounds, saw a man with a knife. I left out the part where I was standing three feet away, watching, invisible.

"Did you see the perpetrator's face?"

"No. It was dark. But he was methodical. Practiced. This wasn't his first time."

I give them what else I can, the victim's approximate age, his clothing, the precise way the killer cleaned his blade, and then I hang up.

My hands are still shaking.

I wait for the sounds of sirens heading toward K Street before I start walking home. The streets are quiet, the late-night emptiness of DC after the bureaucrats have gone home. I walk with my shoulders hunched, making myself small.

Old habits.

My apartment is a fourth-floor walk-up with three locks on the door. I check each one twice before I let myself believe I'm safe.

Not that locks have ever been my real protection.

I strip off my clothes and stand in front of the bathroom mirror, cataloging what I see. Brown hair, gray-green eyes, unremarkable features designed by genetics or God to be forgettable. When I want to be invisible, even visible, I know how.

But someone saw through that tonight.

I can feel you.

I turn off the light and climb into bed with my phone in my hand, watching the news app for any mention of a body found behind K Street. Nothing yet. It's too soon.

Tomorrow I'll go to work. Consult on cases. Analyze the behavior of killers from a safe distance, behind glass and reports and profiles.

And I'll pretend tonight didn't happen.

Just like I've pretended my whole life.