She was referring to using sheets of plastic to lift shoe prints, in much the same way that fingerprints were lifted. The resulting tread pattern not only could suggest shoe size but might show up in the massive footwear database that Rhyme had created at the NYPD years ago, which was still maintained.

‘And I’d say he had his own adhesive roller with him. It looks like he swept up as much as he could.’

‘I hate smart perps.’

No, he didn’t, Sachs reflected. He hated stupid perps. Smart bad guys were challenging and a lot more fun. Sachs was smiling beneath her N95 respirator. ‘I’m going silent, Rhyme. Checking the entrance and exit routes. The manhole.’

She withdrew her Maglite, flicked on the powerful beam and continued down the tunnel toward the ladder leading up to the manhole, noting not a bit of pain from the persistent arthritis that had plagued her for decades; recent surgery had worked its magic. Her shadow, cast by the halogen spot behind, stretched out before her, a distorted silhouette of a puppet. The ground beneath the manhole was damp. This strongly suggested it was how he’d gotten into and out of the tunnel. She noted this fact then continued on, into the darker reaches beyond.

With every step she grew more uneasy. Not because of claustrophobia this time – the tunnel was unpleasant but spacious compared with the entrance shaft. No, her discomfort was because she’d seen the perp’s handiwork – the tattoo, the cutting, the poison. The combination of his cleverness, his calculation and his perverse choice of weaponry all conspired to suggest that he’d be more than happy to hang around and try to stop his pursuers.

The flashlight in her left hand, while her right hovered near the Glock, Sachs continued down the increasingly dark tunnel, listening for footsteps, an attacker’s breaths, the click and snap of weapons chambering rounds or going off safety or cocking.

None of those, though she did hear a hum from one or more of the conduits or the yellow IFON boxes, whatever they were. A faint rush from the water pipe.

Then a scrape, a flash of movement.

Glock out, left hand gripping the Maglite, forearm supporting her shooting hand. The muzzle followed the beam. Sweeping, scanning.

Where?

Sweat again, a thud of heartbeat.

But very different from claustrophobia’s chest-thudding panic. This wasn’t sour fear. This was anticipation. This was hunt. And Amelia Sachs lived for the sensation.

She was ready, finger off the guard, onto the trigger but feather-light; it takes little more than a breath to fire a Glock.

Scanning, scanning …

Where? Where?

Snap …

She crouched.

And the rat stepped blithely out from behind a pillar, looked her way with faint concern and turned, scuttling away.