Danger lurks in every corner of River City. The bodies turning up in the waterway that give the city its name are more than enough proof. Who are these young women? Where did they come from, and how can their killer be caught?A drug bust provides a break in the case for the River City Police Department. A loose-lipped informant tells all: the murdered young women are fighters in an underground mixed martial arts tournament run by Leo Manetti, son of infamous River City crime boss Mike "the Hammer" Manetti. However, the police know that they'll need more than his word to make a case.Detective Sarah Kolchek thought that she was done going undercover. She wants nothing more than to put the dangerous police work behind her and start a family with her fiancé, Dale. Too bad that she's perfect for the assignment. As an ex-MMA fighter, she's asked by her lieutenant to go undercover one more time and gather evidence to bring the killer to justice and in the process, take down Leo, Mike "the Hammer," and the whole Manetti empire. That is, if she doesn't wind up as one of the bodies in the river herself.