Eighteen months ago, Detective Reed Mattox didn't just lose his partner, the woman he met on his first day at the police academy and worked with for the entirety of his career thereafter. He lost his confidante. His sounding board. His support system.

His best friend.

Victim to a senseless shooting during a routine traffic stop, the details of that night are still as elusive to Reed as they were more than a year before. Months of scouring every detail, poring through every resource, have revealed nothing, heightening the guilt he still carries for being more than two thousand miles away at the time.

When the phone rings late one evening, Reed hopes it is the brass within the Columbus Police Department calling to let him know he and his new K-9 partner Billie have been reinstated. That the administrative leave they were placed on in the wake of their last major case has been lifted, freeing them from the personal Hell they've been stuck in for the last couple of months.

What he hears instead is something much bigger, cleaving straight to his core, and perhaps finally allowing them to close a case nearly a year and a half in the making...