Ms. Calculation

Mystery Christmas #1 The body found in the Dunrovin Ranch stables isn't just a crisis for Wyatt Fitzgerald's family or his top priority as sheriff--Gwen Johansen is both the victim's sister...and Wyatt's ex. And in a small town like Mystery, events of the past don't seem to fade. Maybe she'd misjudged his potential when they were younger, but now he could be her greatest ally--and not just in the investigation. That is, if he can work his way around a broken heart. With the killer circling, the clock is counting down on more than Christmas, a time when family means everything and forgiveness is the best gift of all. - Goodreads website