The elevator is one of the slowest rides in the city, and while we descend, Puck paces the confines of the bronze cage, in a hurry to get outside and relieve his aging bladder. I am nowhere near so eager. This late-night descent into the streets charges me with enough adrenaline to keep me alert for the rest of the night. As we emerge from the relative safety of the building, I check both ways down the avenue. That I don't see anyone in no way eases my anxiety. Puck, oblivious, lifts his leg and drowns a weed that has sprung up through a crack in the concrete.

It is actually a beautiful street, edged on this side by graceful limestone buildings and, on the far side, by Prospect Park. All of the buildings but ours have gone co-op over the past ten years, sandblasting the grime from their gargoyles and unfurling fresh awnings onto the avenue. But the quiet prosperity is misleading. This pocket of gentrification is a scant few subway stops from half the projects in Brooklyn and an inviting destination spot for the criminally minded. The length of the avenue is a particular favorite with muggers, because they can hit their target and then disappear into the foresty expanse of the park across the street. Last winter, a man on the second floor was held up at gunpoint right where I'm standing, in the shadow of our awning.

We move into the peachy glow of the sodium streetlights, and Puck shuffles slowly toward the curb. The curb glitters with safety glass, where car windows have been smashed in search of phones and tape decks. I wait impatiently while he sniffs the leg of a newspaper box and then waters it. Next is the bus stop sign, and then the light pole and mailbox on the corner. Usually, this is as far as we go at night, just twenty paces to the corner and back, but it takes a good ten minutes to inspect and mark each stop on the route. When I try to hurry him, he gives me a wounded look and, I swear it, exaggerates the arthritic stiffness in his gait. Then he gives his end of the leash a small tug toward the tree trunks down the slope.

Something is fluttering from a lower limb of the old plane tree. I can't make it out from this distance, but then I notice that the trees all the way down the block are festooned with paper. On closer inspection, they turn out to be crayoned drawings of the trees themselves: row after row of green lollipops, some with bluebirds and yellow ball suns. "Save Our Trees" is lettered in a careful, childish hand across this first one. Taped to the next trunk is another drawing, but its message is lost in the deep shadows.

Early this spring, a utility crew showed up unannounced and started surveying the block to install new pipeline. The project would entail digging into the gnarled root system that underlies the entire length and width of the block. From the city's perspective, the old trees are a nuisance anyway – their roots curdle the sidewalks and push up asphalt – but when they blithely started ribboning off old willow oaks and plane trees, they severely underestimated the depth of the neighborhood's affection for those trees. They also didn't take into consideration that half the newly renovated brownstones are inhabited by attorneys with inflated property values to protect. Wham bam, the city was up to its eyeballs in court injunctions before they could even finish staking.

A sheet of butcher paper has been wrapped around one trunk about eye level and secured with tape. I have to walk around the trunk to read the length of the message: "This tree was planted in 1927. It will take another…"

There is movement in the shadows. I feel the presence of another human being before I see him. A dark silhouette. He is maybe fifteen paces off, coming down the sidewalk in my direction, but even at this distance I can tell he is not one of the attorneys coming home late. When he sees that I have spotted him, his gait becomes exaggeratedly casual.

He is thin, I see now, and his clothes are several sizes too large. They hang off him like a scarecrow. Enormous jeans ride low on his hips and drag at the heels of absurdly large and elaborate running shoes. It is the uniform of clowns and young urban wannabes.

I see him glance around, checking for other eyes that might be watching us. My limbs fill with helium. I tighten my grip on Puck's leash and try to redirect us slowly toward the curb, toward the light, casual, as though I'm not avoiding him, oh no, I just happen to live on the other side of the street. I'm not going to make it, not without running. I stiffen my spine as we prepare to pass one another, and my eyes move to his.

It's him. The guy in my apartment. A small flinch betrays that he recognizes me, too. You fuck. You fucking son of a bitch. Hold a knife on me in my own fucking kitchen. Not again, you shithead. No way, you fucking piece of shit. The words are coming out of my mouth. His cocky swagger wilts, and he edges around me, mumbling something. Once past, he breaks into a light trot.

I drop Puck's leash and yell at him to sit and stay and, I don't know, maybe I'm yelling at the guy to stay, I'm so crazy with rage, I don't know. I follow him. I break into a run and charge after him down the block. I don't know what I'm thinking, my heart is thundering and pumping gallons of blood into my head so I can't think. I just run.

He sprints across Eighth Avenue and I follow, checking for cars, but there is only one and it is too far down the avenue to help or hurt. He cuts left, and we are pounding along Eighth. We cross Fifth Street, then Sixth, then Seventh, and I figure he must be heading for the subway station two blocks ahead. I don't think I'm going to make it that far. There is a painful stitch gathering in my side, and my breath is coming in searing gasps. I have my eyes trained on his back and I can hear him panting, too, but he is also starting to put distance between us. And then he stumbles. His gawky limbs buckle and he flies sprawling onto the pavement. I am on top of him before he has a chance to get up. He flails, and one elbow connects, hard, with my cheekbone. I scrabble back onto my feet and kick him once, feebly, but then when he starts to rise, I kick him again, harder, and again, I don't know how often, until he crumples, shielding his face. I find my breath enough to croak a few more obscenities at him.

"I wasn't doing nothing," he whimpers. "I didn't do nothing to you."

Something is wrong. Something is drastically wrong here. The voice. I have been hearing a voice in my head for the past month – "I got a gun" – the timbre of that voice, every inflection, the curl of each vowel and the thud of every consonant is burnished into my nightmares. This is not the same voice.

I look down at this guy I've been chasing. He is rising slowly, warily, to his knees, one hand cradling his jaw, and though he is the same race and has the same lanky build as my burglar, he is not the same man. For starters, this is a kid, fifteen, sixteen at most. And he's trying not to cry. His mouth is smeared with blood.

He senses the moment has shifted and suddenly springs up and back, turns heel and takes off again, a jagged painful lope punctuated every few feet by a glance backward to see if I am in pursuit.

I feel sick in my gut. I've attacked someone with no provocation, no excuse in the world, and beat him on the street. I am deeply ashamed. I am dust. There are no words for this.

I am squatted on the steps of a brownstone, hunched over and waiting for the earth to swallow me up when a voice hails me from above.

"Are you okay?" An old man, clad in bathrobe and slippers, is standing on the stoop of the brownstone, just inside his doorway. He is framed in the yellow light of the vestibule.

I nod mutely. My throat is closed.

"Do you want me to call the police?" He moves down a few steps, letting the door shut behind him. "I saw him take off. He can't be too far. I can call the police for you. No trouble."