Last week the trap sprang shut. In a packed courtroom in The Hague, the first woman to be indicted by the tribunal pleaded not guilty to charges of genocide and crimes against humanity. Then she was locked in a second-floor cell at The Hague’s detention center. Plavsic’s surrender marked a dramatic victory for chief prosecutor Carla Del Ponte, who has been struggling to erase the perception that the court has been slow in bringing Bosnian war criminals to justice. Plavsic’s detention will almost certainly increase pressure on the main architects of the conflict: fugitives Karadzic and military commander Ratko Mladic. And, if Plavsic cooperates, her testimony could prove vital in building a case against Slobodan Milosevic, who still has not been indicted for his role in the war in Bosnia, which many consider his biggest crime.

Plavsic was an unlikely candidate for infamy. The daughter of prominent academics in the northern Bosnian town of Tuzla, she studied viral biology in Zagreb and earned her doctorate in the United States on a Fulbright scholarship. After decades of teaching abroad and a brief marriage to a Serb lawyer, she became the dean of sciences at Sarajevo University, then a symbol of multiethnic coexistence. But as the contagion of Serb nationalism spread through the former Yugoslavia, Plavsic became a true believer. Some say her deep devotion to the Serb Orthodox Church may have stoked her passions. In 1990 she cofounded the hard-line Serbian Democratic Party (SDS) along with Karadzic. She served as a member of the three-person presidency of the breakaway Serb republic and was present at all key meetings of the Bosnian-Serb command as troops and paramilitary units swept through Bosnia in 1992. Neatly coifed with color-coordinated purses and dresses, she presented a civilized contrast to the male hard-liners in the wartime government. Says Branko Todorovic, president of the Helsinki Committee for Human Rights in the eastern Bosnian town of Bijeljina: “She was a scholar who seemed out of place among a group of ruthless men.”

In fact, Plavsic may have been the most fanatical of them all. At the outset of the Bosnian war in April 1992, she traveled to Bijeljina, after it had been brutally cleansed of its Muslim population. There she planted a famous televised kiss on the cheek of Arkan, the notorious paramilitary commander who had led the assault, and she praised him as “a Serb hero.” In 1993 Plavsic declared that “I would prefer to cleanse eastern Bosnia completely of Muslims” and vowed to pursue the war against them at any cost: “Even if 6 million Serbs perish the other 6 million will live decently,” she proclaimed, quoting a Serb soldier on the front line. Serb troops admiringly called her “The Empress.” Her pro-Serb ideology was so rabid that even Milosevic said she belonged in a mental institution. Slobo’s wife, Mirjana Markovic, once compared her to Josef Mengele.

But Plavsic did an about-face after the signing of the 1995 Dayton accord. Elected president of the postwar Republic of Srpska, Plavsic split dramatically from her fellow hard-liners in 1997. She had discovered through police intelligence that Karadzic was making an illicit fortune smuggling goods into the neighboring Muslim-Croat Federation. Publicly attacking him for corruption, she broke from the SDS and formed her own party. Plavsic declared her willingness to accept Muslim returnees in Srpska and to fully respect the Dayton guidelines. Nationalists threatened her life. Western leaders, desperate to find a partner among Bosnia’s Serbs, went out of their way to embrace her. But in 1998 Plavsic was badly defeated for re-election by an ultranationalist. For the past 18 months she has led a lonely existence in Banja Luka, loathed by hard-liners who view her as a traitor, scorned by former supporters.

Plavsic will likely go on trial next winter; in return for her surrender, sources say, she could be released on her own recognizance until her day in court. Plavsic’s attorney plans to argue that she sincerely believed Bosnia’s Serbs were threatened by the expansionist goals of other ethnic groups, and saw the war as a legitimate form of self-defense. He also maintains that her role in military strategy was minimal. “She had no real power at any period during the war,” says Simic. “She was a floral decoration.” But victims of ethnic cleansing scoff at this. “She’s a criminal every bit as bad as Karadzic,” says Adjiva Sehomerovic, 65, a Muslim whose husband disappeared while in Serb custody in 1993. Plavsic’s arrest must have sent a chill through dozens of other alleged war criminals who still hold positions of power in both the Federation and the Republic of Srpska. Says Miodrag Zivanovic, an opposition leader in Banja Luka: “The message is: you cannot escape justice.”

For the biggest fish, Plavsic’s surrender draws the net tighter. Though Milosevic was indicted by The Hague in 1999 for the ethnic cleansing of Kosovo, the tribunal has been unable to link him directly to war crimes in Bosnia. The reason: Milosevic served as president of Serbia during the Bosnian war and had no formal authority over the Yugoslav Army, which covertly aided the Bosnian Serbs. But Plavsic could provide vital information that Milosevic made key decisions–including which Bosnian villages to target for ethnic cleansing and which commanders to appoint. Last week a Bosnian Serb official involved in negotiations with The Hague for Plavsic’s surrender said that she had agreed to cooperate in the prosecution of Milosevic and Karadzic, but wouldn’t testify against Mladic: she still considers him a war hero. The Hague officials hope that her very presence at the tribunal will set an example. “I would like to see Karadzic and Mladic be as courageous as the woman, and surrender,” says a spokesperson. But with Slobo himself facing imminent arrest in Serbia, their time maybe running out.