Evening at the Hall of Justice, and a mysterious figure walks into the courthouse. The figure bypasses the night guard and enters the courtroom, then replaces the gavel with a special one. The next morning, Judge Maxwell enters the courtroom, calls the courtroom to honor, strikes the gavel, and there's a huge explosion.
Frank is called to headquarters when he hears about the bombing. Ed explains over coffee, doughnuts, and dessert that Maxwell was known for harsh sentences and they're checking the records on recently released prisoners. One of the names, Eddie Casales, rings a bell, but the file shows he was a model prisoner. They have Eddie's last known address and Frank decides to check out the ex-wife. Eddie was divorced when he was in prison and his wife Lana buried herself in charity work. After taking their coats (and donating them to charity), Lana admits that she hasn't spoken to Eddie since the divorce. She pours her heart out to them about her troubles and notes that Eddie has been seeing a floozy named Mimi De Jour.
Ed and Frank go to the Club Flamingo where Mimi performs and talk to her about Eddie. She's worried that Eddie is in trouble and says he was with her at the movies. Eddie comes in and insists they're trying to pin the court bombing on him. He insists he's innocent but Frank warns him not to leave town in case they want to talk to him. Once they're gone, Eddie makes sure that Mimi told the police that he was at the movies.
Back at Police Squad, Ted Olsen has analyzed the bomb and determined that it wasn't the work of a professional. Frank is snappy because of too much caffeine and Ted prescribes decaffeinated. Later that day, Frank is feeling much better, other than the hysterical laughter.
That night, the mysterious figure approaches a parked car and places a bomb inside the engine. The next morning, former district attorney John Simongton comes out and starts up the car, which blows up. Frank arrives at the scene where Ed and Nordberg are already at work. Simongton prosecuted Eddie Casales, and they find a book of matches from the Club Flamingo. They bring Casales in but Eddie can't remember what movie he was at because he claims he dozed off. They have no choice but to let him go because of the circumstantial evidence.
Frank receives a call from Mimi to meet her at the Club Flamingo. She tells Frank that she lied about Eddie's alibi and that he went out somewhere and said it was best she didn't know. Mimi mentions that Eddie dumped Lana, and Frank realizes that contradicts Lana's story. Frank goes to see Johnny the Snitch and pays to find out that Eddie is a Milwaukee Brewers fan with season tickets. Frank calls Lana and tells her that they had to release Eddie, but he knows she and Mimi talked and might go after them. He tells Lana that Mimi has turned down police protection, but offers her protection. Lana turns it down, insisting she's leaving town and isn't in danger.
That night, Ed and Frank are watching Mimi's apartment. The mysterious figure walks toward the building and plants dynamite, then moves down the street to detonate it. Frank finally spots the figure and he and Ed go in. They discover that the bomber is... Lana. She threatens to blow up the entire neighborhood sky high. When Frank refuses to back down, she sets off the dynamite, but nothing happens. Eddie walks over, revealing that he found the dynamite and disarmed it.
Later at the office, Frank explains that Eddie did lie about his alibi. He was up in Milwaukee watching a Brewers game, but crossed the state border in violation of his parole condition. However, the officers decide to overlook it given the circumstances.