A Knight Before Christmas — Alicia Dean

The Three Kings, Book 2
The last thing Heath King wants is to return to Kansas City for the holidays. Being in his home town holds too many bad memories, and now there are new bad memories in the making, among them a sister he never knew about--proof that his father was unfaithful. But the most difficult thing he'll face is running into Nicolette, his best friend's widow -- the woman he's loved since the day he met her.
Before Nicolette Morgan has time to fully grieve over her husband's death, a blackmailer enters the picture, demanding she pay him or he'll ruin the lives of everyone she loves. Nicolette sees no way out until she unexpectedly encounters Heath King. When she turns to him for help, old feelings are rekindled and she realizes she never stopped wanting him.
As Christmas approaches, Heath must find a way to stop the blackmailer...but can he also rescue the love he lost fifteen years ago?