CHAPTER NINETEEN
Thomas Garrett arrived within five minutes, moving with the unhurried confidence of someone who'd spent decades navigating underground passages where haste could get you killed.
He was in his late fifties, Isla guessed, with the kind of weathered features that suggested years of exposure to extreme temperatures and harsh conditions.
His hair was more gray than brown, cropped short beneath a battered maintenance cap, and his hands showed the calluses and scars of someone who worked with tools and hot metal for a living.
"Agents," he said, his voice carrying a slight rasp that reminded Isla of steam hissing through old pipes. "Gary said you needed help understanding the tunnel system. Happy to assist however I can."
Isla stood, extending her hand. His grip was firm but not crushing, and she noted the way his gaze moved between her face and James's with the careful assessment of someone sizing up a situation. "Special Agent Rivers, and this is Agent Sullivan. We appreciate you taking the time."
"Time's about the only thing I've got plenty of down in those tunnels," Garrett said with a half-smile that didn't quite reach his eyes.
He pulled out a chair and settled into it with the ease of someone settling into familiar territory.
"Twenty-three years I've been maintaining that system.
I know every passage, every junction, every place where the heat gets dangerous or the water rises too high. "
"That's exactly the expertise we need," James said, pulling out his laptop. "The city's official maps are incomplete. We need to understand the full scope of what's down there—particularly the decommissioned sections."
Garrett's expression shifted, becoming more serious. "You're investigating the murders. The ones in the tunnels." It wasn't a question. "I heard about Langford—worked with him a few times over the years. And the social worker, and now the doctor. Terrible business."
"Did you know any of the victims well?" Isla asked, watching his face carefully.
"Not really. Langford and I crossed paths occasionally—different departments, different schedules.
He wasn't the friendliest guy, but he knew his job.
" Garrett paused, his fingers drumming once against the table.
"The others, just names from the news. But I'll tell you what bothers me most—whoever's doing this knows the tunnels almost as well as I do. Maybe better, in some ways."
The admission was striking. Isla leaned forward slightly. "What makes you say that?"
"The locations they're choosing. The modifications to the temperature controls.
The way they're navigating through sections that aren't on any map.
" Garrett pulled off his cap, running a hand through his gray hair.
"I've spent two decades documenting passages the city doesn't officially acknowledge exist. And whoever your killer is, they've found the same passages.
They're using the system the way I would—as a tool, a weapon, something with its own logic and rules. "
He reached into the worn canvas messenger bag he'd brought with him and pulled out a bundle of papers held together with rubber bands. "I brought my maps. The real ones, not the sanitized versions the city keeps on file."
Isla accepted the bundle, carefully removing the rubber bands to reveal dozens of hand-drawn schematics on graph paper.
Each page was meticulously detailed, showing not just the main corridors and access points but smaller passages, hidden junctions, areas marked with notes in cramped handwriting.
"Extreme heat—protective gear required." "Flooding risk—check weather conditions.
" "Structural damage—avoid northwest corner. "
"Jesus," James muttered, looking over her shoulder at the complexity. "This is like a completely different system from what we've been working with."
"Because it is," Garrett said. "The official maps show you the bones—the main arteries where steam flows, the primary access points that maintenance crews use regularly.
But the tunnels are more than that. They're a living system, constantly changing.
Pipes corrode and leak. Water accumulates in low spots.
Heat builds up in poorly ventilated chambers.
And the older sections—the ones that were abandoned when they built newer systems—those are like ghost passages.
Still there, still connected to the network, but forgotten. "
Isla spread several of the maps across the conference table, studying the intricate web of passages Garrett had documented.
She could see the three murder scenes marked—Access Point 7, where Langford had died, the abandoned section where Graves had been drowned, and Access Point 14, where Yamamoto should have died before the killer was forced to adapt.
"These locations," Isla said, tapping each murder site in turn. "What do they have in common from a structural perspective?"
Garrett moved closer, his weathered finger tracing paths between the marked points.
"They're all junction chambers—places where multiple passages converge.
That's important because it gives the killer options.
Multiple entry points, multiple escape routes.
You can't corner someone in a junction chamber because there's always another way out if you know the system well enough. "
"And the environmental conditions?" James asked. "The extreme heat in the Langford scene, the water in the Graves scene?"
"Those weren't accidents," Garrett said flatly.
"Whoever set those up knew exactly what conditions they'd find in those specific chambers.
The heat in Chamber D-8 comes from a cluster of high-pressure lines that run through that section—normally regulated by automated controls, but easy enough to override if you have access to the junction boxes.
The water in the decommissioned section accumulates because of poor drainage and condensation from the active pipes running overhead.
It's been like that for years, getting deeper every winter. "
Isla felt a chill that had nothing to do with the December cold seeping through the building's windows. "So the killer is using the infrastructure itself as a weapon. They're not bringing tools or equipment—they're just manipulating what's already there."
"Exactly." Garrett pulled one of his maps closer, pointing to several other locations marked in red ink.
"And if I were planning more murders using the same methodology, these would be my high-risk targets.
Junction E-6 has a steam release valve that could flood the chamber with superheated vapor if activated.
Section H-2 has a carbon monoxide buildup problem—we're supposed to monitor it closely, but if someone disabled the sensors and lured a victim there.
.." He trailed off, the implication clear.
"Show us everything," Isla said, her voice tight with urgency. "Every high-risk location where the system could be weaponized."
For the next hour, Garrett walked them through his maps with the patience of someone who genuinely wanted to help.
He identified seventeen locations that met his criteria—chambers where environmental conditions could be manipulated to create lethal scenarios, junction points with multiple access routes that would allow a killer to escape undetected, sections isolated enough that screams would never reach the surface.
Isla's stomach tightened as the list grew.
Seventeen potential murder scenes, scattered throughout the tunnel network like landmines waiting to be triggered.
They couldn't possibly monitor all of them effectively, not with their limited resources and the killer's apparent willingness to adapt when circumstances changed.
"Mr. Garrett," she said when he'd finished his presentation, "this has been incredibly helpful. But I have to ask—who else knows these tunnels the way you do? Who else would have this level of detailed knowledge?"
Garrett considered the question carefully, his expression troubled.
"Not many people. Most of the newer maintenance workers stick to the active sections, follow the official maps, do their jobs without exploring beyond what's required.
The old-timers who knew the system as well as I do—most of them are retired or dead. "
"But there must be someone," James pressed. "Someone you've worked with, someone you've trained?"
"I've shown my maps to a few people over the years," Garrett admitted.
"Safety inspectors, engineers, the occasional consultant who needed to understand the full scope of the system.
But I've never given anyone copies. These maps—" he gestured to the papers spread across the table "—these are the only complete set that exists. "
Isla exchanged a glance with James, both of them thinking the same thing. If Garrett's maps were unique, if his knowledge was singular, then how had their killer acquired the same intimate understanding of the tunnel system?
"We'd like to keep these," Isla said, indicating the maps. "For our investigation."
"Of course." Garrett nodded. "Keep them as long as you need. I've got most of it memorized anyway."
As he stood to leave, Isla felt compelled to add: "Mr. Garrett, be careful. If the killer knows the tunnels as well as you say they do, they might see you as a threat—someone who could identify them or interfere with their plans."
Garrett's weathered face softened slightly. "I appreciate the concern, Agent Rivers. But I've been working those tunnels for twenty-three years. I know how to stay safe down there."
The words should have been reassuring. Instead, they sent a chill down Isla's spine.