But their paths kept intersecting.
“Detective.” Erin’s voice carried an edge of discovery. “Look at the accelerant placement.”
Lena approached where Erin knelt beside a section of damaged flooring. The fire marshal pointed to a pattern barely discernible in the char, but once Lena saw it, something about it seemed deliberate.
"What am I looking at?" Lena asked, crouching beside her.
"They positioned the accelerant to exploit the building's air circulation system. The flames followed predictable thermal dynamics, but only because someone calculated how they'd behave." Erin's voice carried the enthusiasm of someone explaining their expertise.
Lena found herself watching how Erin lit up explaining the complex fire science. "That sounds like it requires specialized knowledge."
"More than specialized. This is an expert-level understanding of combustion physics." Erin stood, brushing dust and ash from her gear. "What did you find?"
Lena led her to a section near the back wall where debris had been cleared. "I found fragments of what looks like a timing device. Professional-grade electronics, not some crude homemade setup."
Erin examined the evidence, her flashlight illuminating metal fragments and circuit board pieces. "Commercial timingmechanisms, the kind used in controlled demolitions or industrial applications."
"Which means our arsonist has access to professional equipment and the knowledge to use it properly." Lena photographed the fragments from different angles. "This was planned well in advance."
"And the target choice isn't random either," Erin said. "But we'll need to compare all the scenes to see the full pattern."
For the first time since entering the building, Lena looked directly at Erin instead of the evidence. The fire marshal's expression reflected the same concern she felt—two professionals recognizing they were dealing with something more dangerous than either had initially realized.
"We need to cross-reference your fire analysis with the evidence timeline," Lena said. "There’s professional equipment, expert placement, advance planning…"
"And someone with someserioustechnical training," Erin agreed.
They stood in the wreckage, their flashlight beams creating overlapping circles of light. For a moment, the antagonism between them had shifted into professional recognition that they needed each other's expertise to solve this.
Then Erin's radio crackled to life with a status update from the incident commander.
"I need to process this scene completely," Lena said, returning to her camera. "Document the entry point, collect accelerant samples, and map the evidence."
"And I need to complete the structural assessment to determine if there are safety vulnerabilities we need to address at other potential targets."
Lena paused and looked at Erin. "That's preventative work. We need to catch this person before they strike again."
"Understanding their methods helps us predict where they'll hit next." Erin's voice carried an edge. "You can't just chase leads without understanding the technical profile."
"And you can't just analyze burn patterns while more lives are at risk."
The words echoed in the damaged space, both women breathing hard, the momentary collaboration dissolving back into the familiar friction. But underneath the argument, something had changed. They'd worked well together for those few minutes.
"We do this together or we both fail," Lena said finally.
"Together," Erin agreed. "But we need a coordinated approach."
Around them, water continued dripping from the ceiling, reminding them both that they were standing in the aftermath of someone's deliberate attack. Whatever tensions existed between them, the arsonist was still out there planning their next move, and Lena was starting to realize that Erin Vance might be the only person who could help her stop them.
Twenty minutes later, they made their way back through the debris field and out into the night air, their evidence collection complete. The fire crew escort led them carefully around unstable sections, their flashlights cutting paths through the destruction until they reached what was left of the front entrance where both departments waited.
The damage was already done by the time they emerged from the library. Lena could see it in the sideways glances from other officers, the way conversations died as she and Erin approached their respective supervisors. Word traveled fast in emergency response—two departments watching professionals clash not just once but multiple times would fuel precinct gossip for weeks.
Captain Julia Scott stood near the incident command vehicle, her expression carefully neutral as Lena approached. But Lena knew that look. She’d worn it herself when dealing with junior officers who’d let personal issues compromise their judgment.
“How’d it go in there?” Julia asked, though her tone suggested she already knew it hadn’t gone smoothly.
“We found evidence of deliberate planning.” Lena kept her voice level and professional. “The arsonist clearly has technical training.”
