One from the should have read this ages ago pile.
From the Blurb:
To her clients and colleagues, Iris is a therapist in a city psychology practice. But to the police and fire services, she is the Fire Lady – a profiler of arsonists.
After a troubled young man burns down her office, Iris just wants a quiet life. But her peace is shattered when a bomb goes off at a local school. Called in to help, Iris meets James, delusional and dangerous, and Chuck, a lone investigator tracking a serial arsonist he calls Zorro.