His face lit up and he nodded. "Now that you say, yeah. Sort of like cleaning fluid or something." Heat whispered an aside to the EMT to have the ER check him for chloroform.

"What time did this happen?"

"Let's see. I was waiting for lunchtime. About noon." Nikki looked up the block at the bank clock. That would have been almost an hour ago. She felt a hot trail going cold by the minute.

"Sorry, Detective Heat," said the paramedic. "You're going to have to continue this later." Heat thanked Glen Windsor for his time as they wheeled him to the back of the ambulance. Then she appointed one of the uniforms to ride with him and stay by his side at the hospital until she got there.

"Got your gas source right here," said the FDNY supervisor when Nikki came back inside Windsor's Locks, using the door this time. He pointed to the open metal hatch on the heating unit embedded flush in the wall of the shop. He had to shout over the din of the ventilator fans. "See here? Pilot's out, the combustion motor's been disconnected, and somebody pulled the stopper plug out of the test feed joint. Nothing to stop the gas and nothing to burn it off, so it just streamed out and filled the room. I don't want to think about what this could have done."

Detectives Feller, Malcolm, and Reynolds arrived to a.s.sist them in the search for clues. "And by clues, you mean string, right?" asked Rook. " 'Cause it don't mean a thing if it ain't got that string."

"Let's just strike a match and end this," said Reynolds to Malcolm.

The first wave of the search yielded none of the earmarks of the prior crime scenes. As the fire crew declared the atmosphere safe enough to turn off their fans, Heat stared at the one positioned at the open back exit and asked the supervisor to find out if his men opened the door themselves or found it ajar.

"Found it that way," said the uniform next to her. Officer Strazzullo had been among the patrolmen that Heat sent to cover the alley then called back for the evacuation. "When we accessed the alleyway, the back door to the shop stood open about yay." He sectioned about eighteen inches of air with his hands.

"Dang," said Detective Feller to Heat. "Bet you almost had him, and he booked."

Raley asked her, "You think he could have been in here when we rolled up?"

Heat didn't say anything. Instead, she stepped out the open door to the alley. The rest followed, and when they joined her, Nikki stood beside a Dumpster positioned under the fire escape ladder leading to the roof. "Officer Strazzullo, was this bin here when you arrived?"

"Sorry, I don't recall."

"Can I play out this scenario?" asked Feller. "Our killer's inside when you approach, Detective Heat. You interrupt his job on the locksmith-'Uh-oh!'-and flush him out the back door. He hides behind this Dumpster..." The detective acted it out, tracing steps from the back door and hiding behind the bin. "He's here when Strazzullo arrives-this close to a collar-but then the cavalry gets called back out front and he gets away."

"Looks like an escape setup to me," said Ochoa, eyeballing the short distance from the Dumpster lid to the fire escape ladder. "Right after Strazzy got called away to work the evacuation, our boy climbed up on the bin, and poof."

"Could be how he came and went, both," agreed Raley.

Detective Heat boosted herself on top of the bin and ascended the fire escape ladder with teeth clenched. On each rung, she silently voiced anger and frustration at the killer being this close to capture-if he truly had been there.

If.

The others followed her up, and they all walked the roof in a line, searching the flat, grimy surface for anything that told them if.

They found it at the far end of the rooftop. Everyone saw it at the same time. And knew.

One end of a length of red string had been tied to the k.n.o.b of the door to the access stairs and fluttered in the warm breeze. The string had many colors, following the pattern of the other homicides. Red was tied to yellow. Yellow was fastened to purple. And purple was knotted to a new piece of string, this one green.

Heat had already stationed officers to cover all exits of this building, including the stairwell. Silently, she drew her service piece and held it up at-ready beside the door. All but Rook, who was unarmed, did the same and took tactical positions. She nodded, and Detective Feller yanked the door open. Inside, at the top of the steps, stood Officer Strazzullo and his partner. Everyone holstered.

They looked down at the threshold at a broken piece of cinder block. Feller bent, and when he lifted it, a small piece of paper, slightly larger than a postage stamp, that had been underneath it fluttered off in the wind. Raley chased the sc.r.a.p across the roof so it wouldn't blow away, and picked it up with his gloves.

Everyone stood around him in a huddle to see it. The paper, about an inch square, was blank on one side and had a color image on the other. It looked as if a small section from a photocopy of an oil painting had been cut with scissors. All it showed was someone's fingers and knuckles.

Detective Raley used his cell phone and captured a decent close-up image of the hand on the little square of paper before they turned it over to Forensics to fingerprint and lab it. Heat tasked Roach with seeing what they could find out about the painting it had been clipped from. "What you found out about the key saved this guy's life. Find out about the painting, maybe we'll capture our killer."

At Roosevelt Hospital, Heat had to hunt for parking because of all the news vans that had gathered outside the entrance to the Emergency Room. Reporters who were staking out positions for their stand-up pieces for that evening's newscasts saw Nikki and called out to her by name, hollering for comment. She kept her eyes front and badged herself and Rook past the officer at the door.

They found Glen Windsor sitting up with his legs dangling over the side of a bed in one of the trauma bays. He sipped apple juice through a straw, and the color had come back to his face. "How are you feeling, Mr. Windsor?" asked Heat.

He smiled and said, "Lucky to be alive." She returned his smile and thought, Buddy, you have no idea. "Thank you again. I've been thinking. How the h.e.l.l did you know to come help me?"

Heat wasn't sure how much to tell him. On the one hand, he had been the target of a serial killer. But on the other, the press waited, and she wanted to control what got out there. "We smelled gas," she said, truthfully enough.

Windsor said he felt up to it, so she asked him to take her back over his version of the a.s.sault. His account from the crime scene held, and when she moved on to inquire about any unusual contacts, activity, or new people in his life, the locksmith reflected then shook no.

Next she showed him a picture of the key she had found with the last victim. He recognized it immediately. "That's a BiLock. Aussie. Very high-security product. They manufacture rim locks, cam locks, deadlocks, mortise locks, padlocks..." As he went on and on, Rook caught Nikki's eye and turned slightly away to hide his smile. He had often entertained Heat imitating Bubba Blue, reciting to Forrest Gump all the ways to cook shrimp.

When Windsor finished his list, she said, "BiLock told us this is registered to your business."

"That's right, I sell them. Not many yet but it's a good product."

"What I mean, Mr. Windsor, is that this exact key is registered to your inventory. Did you notice it was missing, and if so, is the lock gone, as well?"

He studied the picture and said, "I didn't know anything was missing." He stood up, suddenly worried about his shop. "I'd like to get back and do an inventory."

"We'll do that and send a detective to help. But I have a few quick things to ask."

He calmed, but she could sense his understandable distraction, so she hurried. What she needed to find out was if he had any connection to the other victims, however slight. She showed him head shots of the three prior victims. Roy Conklin meant nothing; same for Maxine Berkowitz, whom he only recognized as a reporter on TV. But when she flashed the picture of Douglas Sandmann, Windsor's eyes popped and he tapped it with his forefinger. "Hey, I know him. Bedbug Doug."

"From his TV ads?" asked Heat.

"Yeah. But I also did some work for him. About six months ago I upgraded all the locks and alarm keypads at his office over in Queens."

Heat and Rook traded glances, each registering a sudden rush of excitement at the break. Nikki tried to remain casual, masking her hope that the victim she saved could shed light on how an active serial killer was choosing his targets. "Glen, did you spend any time personally with Mr. Sandmann?"

"Most definitely. Doug approved the bid and cut the check when I finished."

"May I ask what you talked about?"

"Prices and my time frame. Pretty much what every prospect talks about."

"Anything else? Take a moment to think."

The locksmith took a sip of his juice and stared into the middle distance, then said, "No, sorry. I pretty much just walked him through the job. Nothing memorable. Nice guy, though. Let me pet his dog."

Rook chimed in. "Did you and Bedbug Doug have any friends in common?"

"No, sir."

"Did anyone arrange the job for you?" asked Heat, following Rook's thread. "Maybe a referral from another customer?"

"I wish. Got that account the usual way. Just me making cold calls. Opening the Yellow Pages and smiling 'n' dialing."

With Nikki's breakthrough hopes dimming, she asked him to keep thinking during the next few days. Heat gave him her business card so he could reach her if any detail, however insignificant, came to him.

Detective Feller called to alert her that he was in an undercover taxi he'd borrowed from his old NYPD unit and was standing by at the hospital's side door. The first thing Heat had done when she saw the media setting up was to arrange a discreet exit for Glen Windsor. But before she and Rook could sneak him out of the ER, Nikki got an unwelcome surprise.

"Here's our man!" called Captain Irons across the triage area. She turned as Wally breezed in along with Detective Hinesburg. As her precinct commander approached, Heat could see he not only had on a freshly pressed uniform shirt but wore a dusting of makeup on his porcine face. Like a moth to light, Irons had found the media and arrived ready for his close-up.

After a round of handshakes, back-claps, and a rousing "Glen, way to stay alive," the Iron Man asked Windsor if he would mind stepping out along with him to meet the press. The locksmith cast an anxious look at Heat, but the captain said, "Don't be nervous. You don't have to say anything, just stand with me, I'll do all the talking."

Heat drew her boss aside. "Cap, I really think this is a bad idea. We don't want to spike the ball in the killer's face, do we? And I think the less that's public, the better."

"That's what you always think," said Sharon Hinesburg, inviting herself into the conversation. "Our skipper's taking a lot of s.h.i.t. I say give him a chance to have a moment of victory."

"What victory, Captain?" said Heat, putting her back to Hinesburg. "He's still out there."

"Appreciate your input, Detective. But I am going to step up and let New Yorkers know the Twentieth Precinct is on top of this and saved a life. Excuse us." He left for the main entrance and the news cameras, his arm on the shoulder of Glen Windsor. As they stepped out the sliding gla.s.s doors, Detective Hinesburg turned to look back at Heat and winked.

Rook asked Nikki if she was ready to go. But she paused, struck by the recollection that, in this very emergency room, John Lennon had been declared DOA. Heat moved on, busy making other plans.

She came home that night to find Rook sound asleep on her couch and No Reservations blasting on the Travel Channel. He startled awake when she muted Anthony Bourdain's tetchy pub crawl through Ireland's politically charged saloons. Rook sat up and ma.s.saged his eye sockets with the heels of his hands. The jet lag, he explained, had crept up and walloped him. And with that, he served a natural segue to his French adventure. Nikki didn't seize it.

The awkwardness of dancing around the subject seemed less daunting-and less work-to her than confronting it. Besides, why dance when you can distract? She began a monologue about work. "Randall Feller texted from the locksmith's shop," she said, putting her backup piece, a Beretta 950 Jetfire, in its cubby on the living room desk. "They located the matching lock for the mystery key in his storeroom, so that's that, as far as some potential vic being caged in a room somewhere." She moved to the kitchen and called from behind the open fridge door, "Forensics came up zip, no usable prints. Nothing in the store, or on the doork.n.o.b on the roof, or on the little piece of paper. And get this. In addition to locks, Glen also installs security systems. You think he had even one security cam in his own place? G.o.d. He's like the cobbler whose kids go shoeless. I'm having a beer, you want a beer?" She didn't get an answer, so she closed the refrigerator. And found him standing on the other side of the door. Waiting.

"This isn't going to go away," he said.

Nikki considered that a moment. She opened the fridge and got him a Widmer's to go with hers, then they headed back to the couch.

"Answer me this," she said when they sat down. Each tucked a leg under so they could face each other.

"What have I started here?" He chuckled. "Am I going to get interrogated by The Great Interrogator?"

"Your meeting, Rook. What were you hoping for?"

"To clear the air. So I can allay this irrational-totally irrational-jealous vibe I'm getting from you about Yardley Bell. Jesus, I went to France to help you. Why do I feel like I did something wrong?"

"My question-if I may ask it now-is how did Yardley Bell know you were there? And don't tell me it was coincidence. Did using your pa.s.sport light up her Homeland Security grid, and she followed you across the Atlantic?"

"She suggested we go."

Nikki rocked backward in astonishment. "Oh. Right. Air cleared. Jealousy allayed. Boy, how irrational could I be?"

"See? That's why I didn't tell you. I knew you'd go to the bad place."

"And this doesn't do it?"

"In hindsight, I'll admit I may not have exercised my best judgment."

"What did you exercise?"

"Come on, you know me better than that."

"You, I know. She's another story."

"I told you, Yardley and I are past history."

"To you. But I know her type."

"And what type is that?"

"Obsessive old girlfriends who can't let go. You know what I'm talking about. The ones who drive across the country wearing NASA diapers and have tasers and duct tape in the trunk. Or who write thirty thousand e-mails with veiled threats to rival lovers."

"Yardley sent you an e-mail?"

"No! She doesn't have to. She can hop on a federal Gulfstream to France and rendezvous with you in f.u.c.king Nice."

"Where she provided invaluable support setting me up with Fariq Kuzbari. You should be delighted by that."

"Yeah, look at me. Couldn't be happier."

"You were happy when I told you. Until you found out she was there."

"That's the other thing. Rook, I have been on a mission to keep the feds away from me and out of my case. I've dealt with them a hundred times on a hundred other cases. Their so-called resources come with a price tag. I refuse to let them screw it up with their departmental politics or sell me out in the name of diplomatic expediency. I've kept DHS at arm's length," she said, deciding not to bring up Bart Callan. "Now Agent Heartthrob is sticking her nose in it-and using you to do it. Or vice versa, what's the diff?"

Rook tried to slow things. "Hey? Nikki?" He brought his pitch down and rested a hand on her knee. "This is so not you."

All of it, not just the past few days, but eleven years of it boiled over. She despised it whenever her emotions spilled out, but it was too late to stem this tide. In spite of herself, taciturn, compartmentalized, stoic Nikki Heat blurted her raw vulnerability to him. "I feel alone on this. Everything's coming at me at once. I can't do it by myself."

"Then why don't you want help?"

"I do. Just not from everyone. I can't trust everyone."

"What about me? The idiot who jumped in front of a bullet for you. Do you still trust me?"

There it was. The kind of moment an entire life pivots on as surely as the needle of a compa.s.s.

Nikki didn't answer yes or no. She did something else. Something bigger than she could ever speak. She showed it. Without a word, she rose from the couch and walked to her mother's piano bench to get the codes.

Rook listened intently as Heat told him everything. About the night three weeks ago when she had finally been able to bring herself to play her mother's piano for the first time since the murder. How she opened the music bench after eleven years and took out the music book, the one she had been taught from as a girl. And how, while playing it, she saw something unusual. Small pencil notations between the notes of the songs. He leaned over the book to examine them, squinting, turning his head, trying to make sense of the marks, and she told him what she believed, and, in doing that, answered his question about trust.

Nikki told Rook she believed that these markings were a secret code left by her mother. And that whatever information the symbols hid was the reason she had been killed. "And because all the signs say whatever conspiracy Tyler Wynn is involved in is heating up, I also believe if the wrong person found out we had this code, we'd both be killed, too."

"Swell," he said with a deadpan. "Thanks a lot for dragging me into this." And then they fell into each other's arms and held tight.

A few seconds pa.s.sed. With her face still buried into him, Nikki said, "You're dying to get at that, aren't you?"

"It's killing me."

She pulled away and smiled. "All yours."

Rook didn't hesitate. He swung around to face the coffee table and opened the music book, bending closer, turning his head side to side, squinting some more at the pencil marks. While she let the man she trusted with her life study in peace, her gaze went to the silent TV, where a bartender at the Crown Salon in Belfast pulled Tony Bourdain a perfectly murky pint of Guinness. Nikki had made her leap of faith. At least for the moment, she, too, had no reservations.

They sat up most of the night, working together, banging their heads, trying to figure out the code. They switched from hefeweizen to French Roast, but the coffee only made them more alert, not any more enlightened. Heat answered all of Rook's questions but tried to avoid sharing too much of her path; his fertile imagination would do its best work unconstrained.