Part thriller and part harrowing account of an outrageous, based-on-facts story of official corruption in the former Yugoslavia, "The Whistleblower" is a tense and shattering drama.

The name Kathryn Bolkovac might be familiar to anyone who has heard her accusations over the years that operatives from a United Nations peacekeeping force and an American military contractor, DynCorp International, were involved with sexual slavery in postwar Bosnia.

British actress Rachel Weisz is a sturdy but vulnerable presence as Bolkovac, a Nebraska cop who joined the U.N. mission in Sarajevo to enforce a 1995 cease-fire. The film's script, cowritten by first-time director Larysa Kondracki, employs fiction to fill out some details, but the essential facts of Bolkovac's experience are here.

Appointed head of "gender affairs," the intrepid investigator discovers a broad network in sex trafficking of young, Eastern European women, lured into enslavement for the exploitation of male peacekeepers and DynCorp employees.

Bolkovac is ignored when she brings this scandal to the attention of her superiors, forcing her to pursue the case alone. Meanwhile, resentment toward her efforts builds, creating a tense atmosphere that makes one worry for Bolkovac's safety anytime she's at home or walking to her car.

As a measure of the stifling power of the U.N.'s cover-up, Kondracki brings in a couple of supporting characters who are a bit sketchy but helpfully define what the heroine is up against.

One is an honest but nervous official played by David Strathairn, and the other is Madeleine Rees (a brief but golden performance by Vanessa Redgrave), the real-life human-rights commissioner. Their caution and subdued sympathy toward Bolkovac intensify an air of paranoia.

Kondracki provides glimpses of what sexual slavery looks like, including scenes of women subjected to terror and torture by their minders.

This is not an easy movie to get through, and it certainly casts doubt on the efficacy of well-intended humanitarian missions organized by governments. But Weisz's role as a dutiful crusader in an all-but-lost cause is a reminder of what one person can do.

Tomwkeogh@yahoo.com