The Hacker by Nancy Herkness

Dawn Galioto is an expert in self-defense and the most in-demand personal trainer at her Jersey gym—a perfect position for a woman fighting her way out of a troubled past and the anxieties that come with it. Then, after complaints about baffling Wi-Fi glitches at the gym, Dawn calls in disarmingly hot, high-powered computer consultant Leland Rockwell. If she can trust anyone to fix her on-the-job problems, it’s Leland. As for healing her off-hours fears, time will tell.

The cybersecurity genius of KRG, Leland sees a lot to admire in Dawn. She’s strong, quick-witted, and sexy. And something of a puzzle—one Leland wants very much to solve. If only she’d let him. Every new reveal brings him intimately closer to Dawn, but there’s another, more dangerous riddle to decipher. After going undercover to solve her Wi-Fi problem, Leland’s found a dark workplace secret. As Dawn’s past threatens a burgeoning romance, the deepening mystery they’re discovering threatens their lives.