IN NEW YORK,no wilderness attracts birdwatchers like Central Park. Bigger forest preserves exist in the region, but the glowing green rectangle in Manhattan is home to the most fowl per square acre.

Wielding a pair of Nikon binoculars, the man remained motionless, gazing at a black-capped chickadee. He’d been to Central Park several times and knew the sizable inventory that birdwatchers could draw upon to fill out their collection lists.

He was dressed in casual, late-spring trousers (black) and a windbreaker (navy blue). Trim and athletic, thinning hair halfway to gray, but trimmed and combed carefully into place.

After a moment, the bird flicked away, and he recorded some observations in a small notebook. He continued to scan, slowly, south to north.

“Having much luck?”

The voice, a woman’s, was directed at him. He turned. Pear-shaped and binoculared, she was glancing at the notebook in the man’s hand. Her outfit was red and yellow, as if to make the pointthat camouflage was not a necessary component when bird-watching.

He said, “Saw an ovenbird.”

“No!”

“I did.”

“Did you put it on eBird?”

An online service that included rare sighting alerts.

“Not yet. You?”

She shrugged. “Not much. Just got here. I hear there’s a mute swan. I’ll check the ponds and reservoir later. Where was the ovenbird?”

“Near the museum.”

She turned toward the Metropolitan, across the park, as if the two-tone warbler might be winging its way from there to here at this very moment. Then she turned back and regarded him glancingly. He was hardly handsome, he knew. And his appearance put him around fifty. But he was of fit build and had one special attribute that often appealed: a naked ring finger.

She said, “I saw an American widgeon near the boathouse.”

“Did you?”

Silence fell between them. Then, suddenly, she blurted, “If I were a bird, that’s what I’d be.” She corrected. “Well, a water bird of some kind. Duck, swan, goose. It seems more peaceful. Not a pelican, though. They’re kind of shits. I’m Carol.”

“David.” Holding the notebook in one hand and the Nikon in the other prevented a handshake. Nods sufficed.

A pause. She said, “I don’t think I’ve seen you before.”

Birdwatchers were a close-knit crew. Especially in Manhattan.

“Just transferred here.” The man looked at his phone for the time.

“From where?”

“San Diego.”

“Oh, love it. It’s beautiful there.”

He knew she’d never been.

Another pause. He said, “I better be going. Have a meeting.”

“Nice talking to you. I’m going to go look for that ovenbird. Maybe I’ll see you here again.”

“I hope so,” he said with a smile and turned west, following the sidewalk to another stand of the bushes that were ubiquitous in this part of the park. He gazed past the greenery, without the binoculars, and examined a building across the street, a brownstone—also common here.

He noted, on the sidewalk in front of it, a slim and balding man wearing a loose-fitting dark suit. On his belt was a gold NYPD detective badge. Climbing the stairs, he pressed a bell and looked up at the security camera. A moment later, the door opened.