Many films these days claim to be ripped from the headlines. The Whistleblower really is. Rachel Weisz excels as Kathryn Bolkovac, a Nebraska cop and single mom who thought a 1999 United Nations peacekeeping job in Bosnia might solve her financial problems. Kathryn arrives in Sarajevo to aid the local police in stopping sex trafficking and then finds that the cops, the diplomats and even U.N. employees are a major part of the problem. She finds allies in Madeleine Rees (Vanessa Redgrave), head of the U.N. Human Rights Commission, and Jan Van Der Velde (David Strathairn), an internal-affairs investigator. But corruption is everywhere. Unfortunately, first-time director Larysa Kondracki overplays her hand. The film swings from melodrama to sermonizing, both blunting the human drama that needs to come to the fore. It’s Weisz who holds the ground in a performance of ferocity and feeling.