Nightwaves (2003)

Following the car accident that took the life of her insurance man husband Pete Naylor, Bostonian Shelby Naylor, a magazine journalist who recently graduated from writing fluff pieces to hard hitting investigative stories, requires extensive physical therapy to walk without a mobility device again, let alone partake in her favorite pastime, horseback riding. Although it was the bane of her existence, Shelby, after an incident, is encouraged by the police for her own safety to use what seemed to be Pete's favorite toy, a high-powered police scanner which picks up not only police chatter, but any discussion using radio waves. It is that collateral chatter that Shelby becomes most interested in, she continually hearing the cell phone calls of someone named David, who she will eventually learn is David Birkwell. Most of those cell phone calls are arguments with his wife Brenda, but there are just as many of David with other women, one named Alexia with who he seems to be having an extramarital affair. After Brenda goes missing, Shelby believes the cell phone conversations are evidence of threats. In her sense of wanting to see justice done, Shelby goes to the authorities with the cell phone discussion evidence, some of which she ended up recording. Based on those discussions, Shelby believes David killed Brenda, and the district attorney's office is able to charge him with murder. During the proceedings, Shelby turns to Pete's friend and business partner, Tom Williams, for support, Tom who Shelby may or may not be aware has always had a soft spot in his heart for her. Eventually, Shelby discovers more evidence to make her question her initial belief. Some of that evidence becomes personal to her in the form of a connection to Pete and Tom. Through it all, Shelby's life could be in danger the closer she comes to discovering the truth.