As I watched, he hung up the phone. I could see that it had been an intense, difficult call. I knew those calls—when I dealt with suppliers who were bucking deadlines, or with clients who kept changing their minds about their events. Those calls kept me up at night. But as soon as this Dylan put down the phone, a relaxed smile returned to his face. He called out something I couldn’t hear to two of the volunteers, and one of them tossed a foam football his way. They passed it back and forth for almost a minute. Then he got out of his chair, clapping his hands like a coach. He went from desk to desk, checking in on each of his volunteers. They joked. They argued. An old man showed him something on a computer screen that obviously made him happy, and Dylan kissed the top of his head. He finished his coffee, poured a little more from the pot, and drank it all. He found part of a doughnut in a pink box, and as he took bites of it, he sat on the edge of a desk and checked messages on his phone.

There was nothing special or unusual about any of it. It all looked so casual. So normal. This day, this evening, must have been like any other day for the man who worked inside these walls. That was when it hit me. That was when I understood what made him so different from me.

This Dylan Moran wasn’t running.

All my life, I’d been hurrying to get somewhere, without the slightest idea where that was. But this Dylan was already there. He looked at peace with the ground he was standing on. He would go home to his family tonight, and wake up tomorrow, and his life wouldn’t have changed at all. That was just the way he wanted it.

I felt a malevolent emotion grip my heart again.

Envy, as deep as a well.

Dylan checked his watch and realized what time it was. He was late going home. He looked up with a start, and in doing so, he stared out the windows toward the street. Among the reflections, he saw me. His face did a double-take, and he pushed himself off the desk. Before his mind could truly reconcile the idea that there were two of us, I backed up into the darkness and turned from the window. I crossed the street and took shelter behind the North Park sign, where I was invisible. The door to the building opened a few seconds later, and Dylan came outside. He looked long and hard both ways down the street, but when he saw that the sidewalks were empty, he shook his head and went back into the office.

He didn’t stay there for long.

Just a few minutes later, he reemerged, calling goodbye to the people inside. The incident in the window was obviously forgotten, because he didn’t check the street again. Instead, he turned left, heading toward the river.

Heading toward home.

I followed on the other side of the street. When the traffic cleared, I crossed and fell in behind him. We walked in tandem, half a block apart, but he never looked back. I knew, somehow I knew, that he would take the shortcut home through the park, despite the warnings from Karly that it wasn’t safe. He’d go through the tunnel beside the river, and he’d cut across the open grass where it was pitch black.

The three of us would be together. Dylan. Me. And the killer who was waiting for both of us.

I knew my job. I had to stop that killer once and for all. His journey ended here. This was why I was in this world. I swore to myself that I had no other motives in my heart.

Except I was lying.

I couldn’t hold back dark thoughts bubbling out of that well of envy and desire. Everything this man had, I wanted. His wife. His child. His job. My perfect life was right there in front of me, and all I had to do was take it for myself. If this man disappeared, no one would know. No one would miss him. I’d become him. I would go home and wrap Karly up in my arms, and this world would go on just as it had before. The only price to pay was one sin.

A life for a life.

Eve Brier had whispered to me when this began: You might be tempted to stay.

And not just stay. She’d seen this coming. She’d known that sooner or later, a serpent would dangle an apple in front of me and encourage me to take a bite. You might be tempted to kill that other version of yourself.

Yes, I was tempted. In fact, I couldn’t think about anything else.

Ahead of me, Dylan reached the bridge over the river. He crossed to the east side, still unaware of my presence only a few steps behind him. If he stayed straight, he’d remain on the brightly lit city streets, but the park was immediately below him, beckoning with its solitude and darkness.

I knew that’s where he’d go, because that’s where I would go.

And he did.

He turned onto the park path and skidded down a grassy slope. The empty tunnel led beside the river. For a brief moment, the hill blocked me from his view, and I used that moment to close the distance between us. When I got to the tunnel, Dylan was a shadow moving toward the light, only steps ahead of me.

I should have noticed immediately that the tunnel was dark. The lights had been on when I came this way before, but now they were off. I didn’t realize what it meant. I was too focused on catching up to the man in front of me. I plunged ahead, practically running beside the river, and the noise of my footsteps finally made him aware of me.

He stopped, turning around slowly to see who I was. I stopped, too.

We confronted each other. He stood at the end of the tunnel, lit by the light post and the glow of the street above him. I was still in darkness, my face obscured. We weren’t far apart. If I leaped for him, I’d be on him. He had nowhere to run.

Dylan raised his arms with the fingers of his hands spread wide. He knew that I was a threat, but for now, I was just another Chicago mugger shaking him down. “I’m not armed,” he called. “I’m not going to fight back. What do you want? Money? I don’t have much, but you can have whatever’s in my wallet.”

I spoke to him from the tunnel. “I don’t want money.”

“Then what do you want?”

I tried to speak, but my throat choked up with guilt and indecision. We were alone, no one around but the two of us. It was the perfect moment. Everything I wanted was right in front of me, standing on the trail. All I had to do was take it.

“Talk to me,” Dylan went on. “Are you in trouble? Do you need help? Tell me what you want.”

I couldn’t hold it in. What I said made no sense, not when he couldn’t see my face and see who I was. But I told him anyway.

“I want your life. That’s what I want.”

Fear widened his eyes. He flinched and took a step backward, ready to bolt. I wondered if he was thinking about that earlier moment, looking through the window, seeing his mirror image on the other side of the glass. Did he realize that was me? Could he hear himself in my voice?

“Don’t run,” I warned him sharply, grabbing the knife from my pocket and holding it up in silhouette. “Don’t try it. You won’t get far.”

“Listen to me. I have a little girl. A baby.”

“I know.”

“You know? You know who I am?”

“I know everything about you . . . Dylan Moran.”

“Then what do you want with me?”

“I told you. You’re leading the life I’m supposed to have. And I want it back.”

“What does that even mean?” He narrowed his eyes, trying to see me in the darkness. “Who are you?”

I almost stepped into the light and gave him the answer. I’m you. If I came at him, he’d know who was taking away his world. Before he died, he’d look into my eyes and see the truth. I tightened my grip around the knife handle, feeling it slip in my sweaty fingers. My mouth was dry with desire for what this man had. My legs tensed, ready to move.

But I couldn’t do it. This wasn’t me.

I was trying to take things that belonged to someone else. I’d lost my Karly; he’d kept his. I’d waited to have a child with her; he’d said yes. I could take those things for myself, but in the end, they still wouldn’t be mine. I hadn’t earned them, and this man had. He deserved to keep them, not to have them ripped away by a stranger. I couldn’t steal his life.

I stayed in the tunnel, where I was invisible. The silence between us dragged out.

“It doesn’t matter who I am,” I told him finally. “Go home. Get out of here. Go home to Karly. Go home to your little girl.”

He backed away, unsure whether this was a trick. I stayed in the darkness without moving, watching my one chance at happiness leave me behind. When Dylan got to the top of the slope, he turned his back on me. I knew he would run now, disappearing into the park.

“Dylan,” I called after him sharply.

He stopped, although he was far enough away that I wasn’t a threat anymore. “What is it?”

“Not that way.”

“What do you mean?”

“Don’t go through the park. Stay on the street. If you never want to see me again, stay out of the park at night.”

There was something in the sound of my voice that convinced him. He went the other way. He clambered up the grass away from the trail, and when he was out of sight, he ran. I heard his footsteps pounding above me, as he joined the lights and traffic and people on the street.

He was safe. He’d make it home now.

My grief tasted bitter in my mouth. I felt hollowed out inside. I’d come a long way and ended up back where I started, with nothing to show for the journey. The guilt, the loss, the shame, all distracted me. I wasn’t thinking about where I was, or the darkness of the tunnel that had been lit up when I came this way before. I’d missed the clues I should have seen immediately. I’d forgotten why I was in this world.

I turned around and saw my own shadow.

He buried a knife in my stomach.