Saving Savvie (en Inglés) - Elle James

Assassin Savvie Sanders is ready to call it quits but agrees to one last hit on a bad guy who funds his lavish lifestyle with human trafficking. When she runs into trouble, Savvie calls on old friend, and fellow assassin, Kyla Russell. Her friend sends in Brotherhood Protectors to extract Savvie from danger.

Hunter hasn't allowed himself to fall in love since his high school sweetheart drowned in an accident for which he blames himself. He's spent his life punishing himself for his teenaged girlfriend's loss. When he joins the Brotherhood Protectors Yellowstone team on a mission to rescue a former assassin, he never expected to challenge his vow to never love again. 

The rescue mission gets more complicated when Savvie insists on rescuing others caught in the web of human trafficking.