REACHER AND PAULING caught a cab on Second Avenue and it took them all the way south to Houston Street and then west to Sixth. They got out on the southeast corner and glanced back at the empty sky where the Twin Towers used to be and then they turned north together into a warm breeze full of trash and grit.

“So show me the famous fireplug,” Pauling said.

They walked north until they came to it, right there on the right-hand sidewalk in the middle of the block. Fat, short, squat, upright, chipped dull paint, flanked by two protective metal posts four feet apart. The curb next to it was empty. Every other legal parking spot on the block was taken. Pauling stood near the hydrant and pirouetted a slow circle. Looked east, north, west, south.

“Where would a military mind want to be?” she asked.

Reacher recited, “A soldier knows that a satisfactory observation point provides an unobstructed view to the front and adequate security to the flanks and the rear. He knows it provides protection from the elements and concealment of the observers. He knows it offers a reasonable likelihood of undisturbed occupation for the full duration of the operation.”

“What would the duration be?”

“Say an hour maximum, each time.”

“How did it work, the first two times?”

“He watched Gregory park, and then he followed him down to Spring Street.”

“So he wasn’t waiting inside the derelict building?”

“Not if he was working alone.”

“But he still used the back door.”

“On the second occasion, at least.”

“Why not the front door?”

“I don’t know.”

“Have we definitely decided he was working alone?”

“Only one of them came back alive.”

Pauling turned the same slow circle. “So where was his observation point?”

“West of here,” Reacher said. “He will have wanted a full-on view.”

“Across the street?”

Reacher nodded. “Middle of the block, or not too far north or south of it. Nothing too oblique. Range, maybe up to a hundred feet. Not more.”

“He could have used binoculars. Like Patti Joseph does.”

“He would still need a good angle. Like Patti has. She’s more or less directly across the street.”

“So set some limits.”

“A maximum forty-five-degree arc. That’s twenty-some degrees north to twenty-some degrees south. Maximum radius, about a hundred feet.”

Pauling turned to face the curb square-on. She spread her arms out straight and forty-five degrees apart and held her hands flat and upright like mimed karate chops. Scoped out the view. A forty-five-degree bite out of a circle with a radius of a hundred feet gave her an arc of about seventy-eight feet to look at. More than three standard twenty-foot Greenwich Village storefronts, less than four. A total of five establishments to consider. The center three were possibilities. The one to the north and the one to the south were marginal. Reacher stood directly behind her and looked over her head. Her left hand was pointing at a flower store. Then came his new favorite café. Then came a picture framer. Then a double-fronted wine store, wider than the others. Her right hand was pointing at a vitamin shop.

“A flower store would be no good,” she said. “It offers a wall behind him and a window in front of him but it wouldn’t be open at eleven-forty at night.”

Reacher said nothing.

“The wine store was probably open,” she said. “But it wouldn’t have been at seven in the morning.”

Reacher said, “Can’t hang around in a flower store or a wine store for an hour at a time. Neither one of them offers a reasonable likelihood of undisturbed occupation for the full duration of the operation.”

“Same with all of them, then,” she said. “Except the café. The café would have been open all three times. And you can sit for an hour in a café.”

“The café would have been pretty risky. Three separate lengthy spells, someone would have remembered him. They remembered me after one cup of coffee.”

“Were the sidewalks crowded when you were here?”

“Fairly.”

“So maybe he was just out on the street. Or in a doorway. In the shadows. He might have risked it. He was on the other side from where the cars were parking.”

“No protection from the elements and no concealment. It would have been an uncomfortable hour, three times in a row.”

“He was a Recon Marine. He was in prison in Africa for five years. He’s used to discomfort.”

“I meant tactically. This part of town, he would have been afraid of getting busted for a drug dealer. Or a terrorist. South of Twenty-third Street they don’t like you to hang around at all anymore.”

“So where was he?”

Reacher looked left, looked right.

Then he looked up.

“You mentioned Patti Joseph’s place,” he said. “You called it an aerie.”

“So?”

“What’s an aerie?”

“It’s an eagle’s nest.”

“Exactly. From the Old French for lair. The point is that Patti is reasonably high up. Seven prewar floors, that’s a little above treetop height. An unobstructed view. A Recon Marine wants an unobstructed view. And he can’t guarantee that at street level. A panel truck could park right in front of him at the wrong moment.”

Lauren Pauling turned back to face the curb and spread her arms again, this time raised at an angle. She mimed the same karate chops with her hands. They bracketed the upper floors of the same five buildings.

“Where did he come from, the first time?” she asked.

“From south of me,” Reacher said. “From my right. I was facing a little north and east, at the end table. But he was coming back from Spring Street then. No way of knowing where he had started out from. I sat down, ordered coffee, and he was in the car before they even brought it to me.”

“But the second time, after Burke switched the bag, he must have been coming straight from the observation point, right?”

“He was almost at the car when I saw him.”

“Still moving?”

“Final two paces.”

“From what direction?”

Reacher moved up the sidewalk to where he had been after strolling around the corner from Bleecker. In his mind he put a green Jaguar beyond Pauling on the curb and pictured the guy’s last two fluid strides toward it. Then he lined up the apparent vector and checked the likely point of origin. Kept his eyes on it as he stepped back to Pauling.

“Actually very similar to the first time,” he said to her. “North and east through the traffic. From the south of where I was sitting.”

Pauling adjusted the position of her right arm. Brought her hand south and chopped the air a fraction to the left of the café’s most northerly table. That cut the view to just a slim section of the streetscape. Half of the building with the flower store in it, and most of the building with the café in it. Above the flower store were three stories of windows with vertical blinds behind them and printers and spider plants and stacks of paper on their sills. Fluorescent tubes on the ceilings.

“Office suites,” Pauling said.

Above the café were three stories of windows filled variously with faded drapes made of red Indian cloth, or macramé hangings, or suspended discs of stained glass. One had nothing at all. One was papered over with newsprint. One had a Che Guevara poster taped face-out on the inside of the glass.

“Apartments,” Pauling said.

Jammed between the flower store and the café was a blue recessed door. To its left was a dull silver box, with buttons and nameplates and a speaker grille. Reacher said, “A person who came out that door heading for the fireplug would have to cross north and east through the traffic, right?”

Pauling said, “We found him.”