Hot Pursuit by Suzanne Brockmann

Alyssa Locke is no stranger to dealing with danger. As team leader of the nation's number one personal security company, Troubleshooters Incorporated, she's seen more than her share of action, survived plenty of close calls, and holds her own with the best of them and against the worst of them. Guarding lives is her game, and no one plays it better. But her toughest challenge will be protecting herself from a serial killer she's been after for years, a fiend who is determined to make her his ultimate trophy. The assignment was supposed to be an easy one: teach self-defense techniques to a newly elected congresswoman and her chief of staff after a political controversy makes them the target of death threats. But among the blizzard of hate mail from hotheads and cranks are the terrifyingly familiar taunts of the sadistic multiple murderer known as The Dentist. Mysteriously silent after a decade-long killing spree, he has suddenly resurfaced, attracted by Alyssa's growing celebrity and the diabolical desire to turn the tables on his pursuer.