Grant Frost is a corrupt top-ranking officer of the Chicago Police Department's east precinct and the main antagonist of the 1998 Warner Bros. film The Negotiator.
He was portrayed by Ron Rifkin.
Frost appears calm, friendly and wise to his colleagues, but deep down in his soul, he is actually a corrupt, heartless and sadistic monster.
After Danny Roman takes down a man holding his own daughter hostage at gunpoint, Frost congratulates him at their Police Chief Al Travis' 60th birthday party. Roman's partner and best friend Nate Roenick tells him about how several of their fellow officers have been embezzling money from the department's disability fund. He also says that inspector Terence Niebuam of Internal Affairs is somehow involved. That night, Roenick waits at the park in his car for Roman to tell him about his informant, but Frost in disguise approaches Roenick's car and shoots him dead, before hurling the communicator, and the gun in the lake. Frost scampers off as Roman arrives at the scene where he lands in hot water with the police as they arrive.
Following the incident, Roman is accused of murdering his partner, despite Roman telling his colleagues that he's innocent. As Frost's hidden plan goes, Roman is stripped of his badge and gun when the police find an offshore bank account's papers with a deposit equal to one of the amounts of the money that was defrauded from the disability fund.
Unfortunately for Frost, Roman holds him hostage along with Niebaum, his assistant Maggie and con man Rudy Timmons. With the building evacuated and placed under siege by his own CPD unit and the FBI, Roman only wants to talk to Chris Sabian, the city's other top negotiator. Roman believes that he can trust Sabian, because he talks for as long as possible, sees tactical action as a last resort and being from another precinct eliminates him as a suspect in the disability fund scheme.
When Sabian arrives, Roman issues his conditions: finding both Roenick's informant and killer, his badge brought to him and a department funeral if he dies. When Sabian is summoned up, He sees Roman holding a frightened Timmons. When Sabian asks why he's here, Roman reveals what Roenick told him and because both negotiators only met once before that sometimes strangers are the only people that can be trusted after one's friends betray them. Just then Roman's squad hastily attempts a breach that goes poorly, resulting in two additional SWAT officers becoming hostages. After Sabian makes it back down, he clashes with Travis, who ordered the Breach and Commander Adam Beck, who justifies the attempt and tells Sabian that he doesn't know Roman as well as they do. Sabian says that Roman's Squad will solve the situation his way, or he'll leave and let the FBI take over. Travis relents, gives Sabian full command and introduces him to the team.
In order to get the authorities to take him seriously, Roman pretends to shoot and kill one of the officers from the failed breach. Roman trades Frost to Sabian in exchange for restoring the building's electricity, having been turned off after the "execution". With help from Maggie and Timmons, Roman accesses Niebaum's computer and pieces together the scheme: corrupt officers submitted false disability claims that were processed by an unknown insider on the disability fund's board. He also discovers recordings of wiretaps, including a conversation that suggests Roenick was meeting his informant before he died. Sabian, using the information Roman provided, claims to have located Roenick's informant in a bid to get Roman to release the other hostages. Roman realizes Sabian is bluffing when Niebaum's files reveal Roenick himself worked for IAD and was the informant.
Roman's precinct is angry at Sabian for the deceit, but Sabian says he doesn't who's innocent. Roman's wife Karen is also mad and attempts to Leave, but Sabian tells her that he doesn't know who he can trust. While Sabian talks to Karen, Roman threatens to expose Niebaum to gunfire from his office window. A frightened Niebaum then admits that Roenick gave him wiretaps implicating three of Roman's squad mates in the embezzlement scheme, Allen, Hellman and Argento. When Niebaum confronted them, they bribed him to cover up their crimes. He adds that they attempted to bribe Roenick, who refused and was killed because of it. Niebaum says that he doesn't know who the inside ringleader is, but that he has the taps somewhere safe. The same corrupt officers have secretly entered the room via the air vents under the pretext of being part of a team to take Roman out in case he started killing hostages and upon hearing Niebaum's confession, they open fire and kill Niebaum before he can reveal where he has hidden the wiretaps corroborating their guilt. Roman fights back, but the sound of the gunshots cause Travis and Beck to initiate another breach. Sabian having heard the gunshots attempts to terminate the breach while Roman single-handedly fights the 3 corrupt squad members and the good ones off using the flashbangs he seized from the officers in the previous failed breach.
Upon hearing that Niebaum was killed when he walked out to talk to Karen, Sabian is furious, but Beck insists that his men had to respond and believes that Niebaum's death was an accident. Believing that Sabian and the police can't resolve the situation anymore, the FBI assume jurisdiction over the operation, cease negotiations, relieve Sabian of his command and order a full breach. Sabian now believes in Roman's innocence and heads up to warn him. Believing he can no longer prove he's innocent, Roman prepares for his eventual arrest. Maggie then reveals that Niebaum also worked at his house and that he could've kept Roenick's taps there. When Sabian comes up, He warns Roman about the FBI coming up. Roman asks if Beck ordered the breach, to which Sabian says it was, but that Beck thinks that Roman fired first and his men responded with Niebaum's death being an accident. However, Roman shows Sabian that Niebaum was murdered as he has 3 bullets in his center-mass. Roman then shows Sabian the officer he supposedly killed is still alive. Sabian gives Roman a chance to prove his case: while the FBI and SWAT team raid the building and rescue the hostages, Roman escapes disguised in the officer's SWAT uniform. Roman and Sabian proceed to Niebaum's house, but are unable to find the wiretaps on his computer. The police arrive and the three corrupt officers enter the house, but they back off as Frost enters and tries to talk Roman down. Sabian observes Frost discreetly taking a loaded gun from one of the corrupt officers and realizes that Frost is the ringleader of the conspiracy, the insider on the disability fund and Roenick's killer.
In front of Frost, Sabian seemingly shoots Roman dead and offers to destroy the "evidence" they have uncovered in return for a cut of Frost's take. Frost agrees and effectively makes a full admission to his and the three officers' crimes. He then destroys the floppy disks and shoots Niebaum's Computer.
When Frost exits the house and tells the police that Roman was killed, he discovers that Sabian only wounded Roman, who used a police radio to broadcast his confession. Humiliated, Frost attempts to commit suicide, but Beck foils it by shooting him in the shoulder. As Beck handcuffs Frost, Sabian helps the wounded Roman out of the house. Roman prepares to shoot his enemy for the setup, but gives the gun to Beck before returning in pain as Frost and the other corrupt officers are taken into custody and eventually imprisoned for life for their crimes.