With his back to her still, he slowly lifted his hands. As his sleeve rode up she got a glimpse of a red tattoo of some kind on his left arm, starting at the back of his hand and disappearing under his coat. A snake, a dragon?

He was raising his hands, yes, but not dropping the backpack.

Shit. He’s going to rabbit.

And, sure enough, in an instant, he tugged his hat down into a ski mask and leapt forward, grabbing the woman, spinning her around. He got his arm around her neck. She cried out and struggled. Her dark eyes were wide with fear.

Okay. He’s Unsub 11 5.

Sachs eased forward slowly, the blade sights of the Glock searching for a clear target.

Couldn’t find one. Thanks largely to the panicked hostage, who was struggling to get away, kicking and twisting. He pressed his face close to her ear, apparently whispered something and, with wide eyes, she stopped struggling.

‘I have a gun!’ he shouted. ‘I’ll kill her. Drop your gun. Now.’

Sachs called back, ‘No.’

Because you never dropped your weapon, you never went off target. Period. She doubted he had a gun – because he would’ve pulled it out and started firing by now – but even if he did, you never lowered your aim.

Sachs rested the sights on the new moon of his head. It was an easy shot with a static target but he was walking backward and sideways and kept ducking behind the hostage.

‘No, please don’t hurt me! Please!’ the woman cried in a low voice.

‘Shut up!’ the unsub muttered.

Reasonably, Sachs said, ‘Listen, there’s no way you’re getting out of here. Raise your hands and–’

A door nearby opened and a slim man in blue scrubs stepped into the corridor. It was just enough of a distraction to draw Sachs’s eye for an instant.

And that  was enough for the unsub to seize his chance. He shoved his hostage directly toward Sachs and, before she could sidestep and draw a target, he crashed through another doorway and vanished.

Sachs was sprinting past the woman in the navy suit. Terrified, she stared with wide eyes, backing up against the wall.

‘What was he–?’

No time for back and forth. Sachs flung the door open and peered in fast. No threat, no target. She shouted over her shoulder to the woman and the medico, ‘Get back to the lobby. Now! Wait there! Call nine one one.’

‘Who–?’ the hostage called.

‘Go!’ Sachs turned and eased through the doorway the unsub had just disappeared into. She listened. A faint click – from below. Made sense; he wasn’t going to escape from the upper floors. Unsub 11 5 was their underground man.

Sachs hadn’t come here on a tactical mission so she didn’t have a radio but she pulled her iPhone out and called 911. It was easier than going roundabout to Central Dispatch. She reported a 10–13, officer needing assistance. She supposed the hostage and the hospital worker might be calling too but they could also simply have vanished, not wanting to get involved.

Down another flight of stairs. Steady but slow. Who’s to say the guy hadn’t clicked the ground floor door latch to fool her and then returned to snipe away with the pistol he did, in fact, have in his pocket?

Sachs had never thought this trip would actually end up in a sighting of the unsub. She’d come here simply to see if any staffers had spotted anyone fitting the perp’s description. Rhyme had speculated that there might be an attack at this hospital. Terry Dobyns’s profile was that, as an organized offender, the unsub would plan the attacks ahead of time. That meant some of the trace they’d found at the Chloe Moore scene might have come from the sites of future poisonings.

Ron Pulaski’s find forty minutes ago was that the Inwood marble trace Sachs had collected was unique to this portion of Manhattan and that explosives permits had been issued to the general contractor building a new wing of the Upper Manhattan Medical Center. Other trace – the industrial cleanser quats and the adhesive that could be used in bandages – also suggested that he’d been inside the hospital to plan his attack on victim number two.

Sachs had hardly expected to actually interrupt him.

Breathing deeply, she paused at the fire door, pushed it open, dropping into a combat shooting pose. Swiveling back and forth. This was the morgue level; there were four employees in scrubs chatting and sipping coffee, standing beside two covered gurneys.

They turned, saw the gun, then Sachs, and went wide eyed, frozen.

She held up her shield. ‘White male in dark coat. About six feet, stocking cap or mask. Slim build. Come by here?’

‘No.’

‘How long you been here?’

‘Ten, fifteen min–’

‘Get inside and lock the door.’

One attendant started to push the gurney through the door. Sachs called, ‘Only the live ones.’

Back to the dim stairwell. Down more stairs. She hit the lowest sub basement. He had to’ve come here.

Go.

Fast.

When you move, they can’t getcha …

She pushed through the door, swinging the muzzle right and left.

This floor was deserted, devoted mostly to infrastructure and storerooms, it seemed.

She kept swiveling, right, left. Because in the back of her mind was the persistent thought that maybe this wasn’t an escape at all. Maybe it was a trap. Maybe he was hiding here to kill a pursuer.

She remembered the line from the book Serial Cities , about Rhyme:

Experts in law enforcement universally voice the opinion of Lincoln Rhyme that his greatest skill was his ability to anticipate what the criminals he’s pursuing will do next.

Maybe Unsub 11 5 was anticipating too.

Terry Dobyns had also suggested that he might target the police.

As her eyes oriented to the dimness, she examined the corridor. He couldn’t go to the left – that was a dead end. To the right, a sign announced, was the tunnel that led to the doctors’ office building.

He could either escape that way … or lie in wait for her.

But nothing to do other than go for it.

Knuckle time …

She started in that direction.

Suddenly a figure appeared in front of her, coming down the tunnel. She paused, plastered herself against the wall, aiming her weapon high but in the general direction of the man.

‘Hey,’ he called. ‘I can see you there. You police?’

A large African American dressed in a black rent a cop security outfit – more intimidating than an NYPD uniform – walked closer. ‘I can see you! Officer.’

She whispered harshly, ‘Come here! Get under cover. We’ve got a perp somewhere.’

He joined her and they both pressed against the wall.

‘Amelia.’

‘I’m Leron.’ The man had quick eyes and he took in the hallway. ‘I heard a ten thirteen.’

‘Heard?’

‘Gotta scanner.’

‘Backup’s on their way?’

‘Right.’

She noted he had a Beretta Nano on his hip, a small gun, 9mm, and accurate enough under good conditions if you mastered the long trigger pull. Unusual for a hospital guard to be armed. She noted that he hadn’t drawn it. No need, no target. This explained him.

‘You were in?’ she asked.

‘Nineteenth.’

One of the Upper East Side precincts.

‘Patrol. Retired, medical. Diabetes. That sucks. Keep your weight down.’ He was breathing hard. ‘Not that you–’

‘You came from the doctors’ office building?’

‘Yep. Drew that detail today. Security in the hospital called me.’ He looked behind her and snickered. ‘None of the brothers I work with decided to come take a look see. Ha.’

‘So he couldn’t’ve gotten out that way.’

‘Nope. Not past me.’ Leron scanned again, behind them, to the left, then to the right.

So 11 5 was here somewhere near, then. But there weren’t many places to hide. There were only a few doors and most of them, storage or electrical and infrastructure, were padlocked.

Leron whispered, ‘Backpack.’

‘Right.’