"Uh-huh." Mike nodded. Miriam-what was her other name? "What's this got to do with the time of day?"

"Well." Pete looked embarrassed. "I asked him how he thought it had worked, and that was when he got agitated. Said you'd told him something about him being in military custody now? So I tried to get him calmed down, told him it wasn't what it sounded like. But he wasn't having it. And at about five in the morning he went missing. Do I have to draw you a diagram?"

"No," said Mike. He sighed. "I knew this military thing was a bad idea."

"Yeah, well. Which of us is going to tell Smith?"

They found the colonel at the security checkpoint by elevator bank B, talking to one of the guards. He didn't look terribly happy. "What are you doing here?" he demanded.

"I've got a hypothesis I'd like to test, sir. I think Matt may still be in the building. Did we catch him leaving?"

"That's what I was just ascertaining," said Smith. He glanced around irritably. "Get me…" He snapped his fingers, searching for a name-"Sergeant Scoville, mister."

"Sir." The guard pulled out his walkie-talkie and began talking to someone.

"So." Smith pointed a bony finger at Mike. "Explain."

"Client Zero is no dummy. He knows he's upstairs. He decided he wants to take a walk. We can be fairly sure he can move between floors but he's not on camera, so either he's been holding out on us-and I don't believe he's got what it takes to hack our sensors-or he's gone to ground. My bet is either under the false floor or over the suspended ceiling, probably on the twenty-third but possibly on the twenty-fourth or twenty-fifth floors. He probably ran into the security zone on the twenty-second and bounced. Now he'll be waiting for an opportunity to go elevator surfing or a chance to slip outside while we're distracted."

"Okay. Now tell me why he's doing this. Where's he likely to go?"

Mike glanced at Pete. "I think he's breaking out because he thought he was looking at a comfortable relax-a-thon in the Witness Protection Program, and a new identity afterward, with us to protect him from his former associates. Unfortunately, once Dr. James switched him to military custody we lost track of the WP program and his new identity, and he finally twigged that he was one step away from being given the whole unlawful-combatant treatment. As for where he's going-I bet he's got his own spare identity stashed away, from before he decided to come in. It won't be as good as what we could have given him if we'd kept him in witness protection, but it beats being a ghost detainee."

"Right." The guard offered Smith his handset. "Jack? Our current best guess is that the target's still in the building, above the security zone on ten. My top priority is, I want you to secure the entry zone and the lobby. Nobody leaves the building even if a Boeing flies into the top floor: our target may try to provoke an evacuation so he can escape in the crowd. I want a security detail to start on floor ten and work their way upstairs, one level at a time, until they get to the roof. They will need torches, floor-tile lifters, and ladders because they're going to check the crawlways and overheads, and they need to be armed because our target is dangerous. How soon can you get that started? How many bodies have we got up here anyway?" He listened for a few seconds. "Damn, I'd hoped for more. Okay, assemble them. Smith out." He glanced back at the two DEA agents. "Right. Any other suggestions?"

Mike took a deep breath. "Is he still valuable to us, if we can get him back?"

"Possibly." Smith stared at him. "Your call, son."

Time stood still. "I need to work on my grammar," Mike said slowly. "But of course, after CLEANSWEEP we'll have more subjects to work with."

Smith held out his hand for the walkie-talkie, watching Mike's face as he spoke: "Sergeant? Change of plan. Hold the floor sweep, I don't think we've got enough people to risk it, if the target manages to arm himself… Instead I want you to stand by to execute code BLUEBEARD. That's BLUEBEARD. I'm going to make an announcement in a couple of minutes. If the fugitive doesn't give himself up, we'll execute BLUEBEARD, then ventilate and search the place afterward."

Pete looked shocked. Mike elbowed the younger agent in the ribs to get his attention. "Go get us all respirators," he said. Smith nodded at him. "You really going to do it, sir?"

Smith nodded again. "We need to test the security system, anyway."

"Ri-ight." The desk guard was watching nervously, as if the colonel had sprouted a second head. Mike grimaced. "I love the smell of nerve gas in the morning." Pete reappeared and handed over a sealed polythene pack containing a respirator mask and a preloaded antidote syringe.

"It's not nerve gas, it's fentanyl," Smith corrected him. "Where's the PA mike on this level?" he asked the desk guard.

"Fentanyl is a controlled substance," said Pete, a conditioned reflex kicking in.

Mike looked round edgily. BLUEBEARD was a last-ditch antiterrorist defense; on command, compressed gas cylinders plugged into the air-conditioning on each floor would pump a narcotic mist throughout the building. Sure, there was an antidote, and the ventilator masks ought to stop it dead, but the only time it had ever been used for this purpose-in Russia, when a bunch of Chechen terrorists had taken a theater crowd hostage-more than a fifth of the bystanders had been killed. Gas and confined spaces did not mix well.

"Relax, boys." Smith looked bored, if anything. "If you're thinking about that Russian thing, forget it-they didn't have respirator masks there. You're perfectly safe." He pulled the gooseneck PA mike toward his mouth and hit the red button. "Is this thing-yes, it's live." His voice rumbled through the corridors and floor, amplified through hidden speakers. "Matt, I know you're in here. You've got five minutes to surrender. If you want to live, come out from wherever you're hiding, and go to the nearest elevator bank. Hit the button for the tenth floor, then lie down on the floor of the elevator car with your hands on your head. This is your only warning."

He killed the PA and turned to the walkie-talkie: "Okay, you heard me, Sergeant. Fifteen minutes from my mark, I want you to execute BLUEBEARD on all floors above ten. You've got ten minutes from right now to do a cross-check on all personnel and make sure they're ready. Antidote kits out, boys. Over."

Smith unsealed his respirator kit. "What are you waiting for?"

"The broken window on the twenty-third," Mike said slowly. "Has it been repaired? And has anyone secured the window-cleaning system?" He opened the packaging around his respirator as he spoke, peeling the polythene wrapper away and yanking the red seal tab to activate the filter cartridge.

"The-" Pete's eyes narrowed.

"We've agreed Matt's not stupid. He probably guessed we'd have something like BLUEBEARD. Maybe he broke the window because he wanted fresh air to breathe?" Mike pointed toward the nearest outside wall. "That got me thinking. Someone's got to clean the windows, haven't they? That means a motorized basket, right? Maybe he figured he could ride it down past the security zone while we're busy trying not to choke ourselves?"

"Point." Smith began to reach for the walkie-talkie again.

"How about Pete and I check out floor twenty-three?" Mike asked, pulling the mask over his head. "We've got respirators, we're armed, we can take a walkie-talkie. More to the point, maybe we can talk him down. Is that okay by you?"

Smith thought for a moment. Finally he nodded. "Okay, you have my approval. Stick together, don't take any risks, and remember-I'm not going to cancel BLUEBEARD if he gets the drop on you. Especially not if he takes one of you hostage. Understood?"

"Yes." Mike glanced at Pete, who nodded.