Dark Horse (#1)by Tami Hoag

Ex-cop Elena Estes once worked for the narcotics division in Florida- until she took one risk too many. Her life shattered, she lives in a self-imposed exile where no one can reach her. But that's about to change when a twelve-year-old girl asks Elena to find her older sister. The wealthy Palm Beach jorsey set into which Erin Seabright has disappeared is a long way from a cop's world...but it's even more dangerous. Elena will need all her street smarts to survive the shadow side of a glamorous sport. Here a killer will lead Estes down a twisted trail of decadence and deceit and murder. A race against time and evil. A race in which Estes is once again the dark horse, where more than just her own life is at stake... and no one is betting on her to win.