A serial killer in New York's South Bronx district is targeting clients of local sex workers. The victims, all male, are either burned alive or beaten to death. With the body count mounting and no real leads, the FBI decides to put someone in undercover.  Enter rookie agent Shannon Ames. Suited for deep cover work because she is single and without family ties, Shannon is young enough to pass herself off as a working girl. More importantly, she is smart, energetic, and determined. Her superiors know she'll do whatever it takes to crack the case.   But spending her nights on the streets as she hunts for the killer takes its toll. Shannon's personal life is falling apart. and her strong moral core is being tested as never before. She begins to feel as if the case is eating her alive. As it becomes clear that she herself is on the killer's radar, Shannon realizes she's up against something truly terrifying—a monster who wants to see her forever marked with his sign of evil.