American policewoman Kathryn Bolkovac (Rachel Weisz) has just accepted the offer of a lifetime - to join the United Nations peacekeeping effort in Bosnia. Quiet and determined Kathryn has dreams of making a difference in a country struggling to emerge from its former Yugoslavian existence.
However, when she arrives she is exposed to horrors that come from a wholly unexpected direction. She bears witness to sex trafficking and corruption from the very people supposed to be solving Bosnia's issues - a private security firm employed by the UN.
Shocked and sickened, Kathryn quickly goes to her superiors but comes up against inexplicable resistance. She gains few allies, including colleague Peter Ward (David Strathairn) and human rights official Madeleine Rees (Vanessa Redgrave). With little support but much resolve, she decides to go after the big fish but, swimming upstream in dangerous waters, it is going to prove tough to catch anyone at all.