Long-time bootlegger and mobster Al Fusary is driving through the night with his bodyguards when the police pull him over. However, when they point out who they're transporting, the two officers pull out their guns and shoot everyone in the car.
Later, private investigator Peter Gunn attends Fusary's funeral. Lt. Jacoby is there and comes over briefly to chat with Gunn, wondering why he's there. Gunn remains non-committal and the lieutenant leaves. Three mobsters—George Fallon, Dave Green, and Henry Ives—come over and Fallon explains that he'll be taking over now that Fusary is dead. He suggests that he'd like to make an arrangement with Gunn, who isn't interested.
After the funeral, Gunn goes to Mother's, a high-end nightclub, and tells Mother about Fallon's officer. Mother figures that Fallon knocked off Fusary so he could take over as head of the underworld, and they wonder how Fallon managed to kill off Fusary in the middle of town. As they talk, the club's feature act, Edie Hart, performs a number. Gunn is more interested in her than in Mother's concern that Fallon will demand protection money from her. He tells her that he'll talk to Fallon and get him to lay off. As they talk, Green enters the club and buys a drink.
Gunn goes out onto the roof and Edie joins him once she's done with her number. She points out that he's been out the last few nights and that she's missed him, and wonders if he ever misses anyone. They talk briefly about their relationship, what there is of it, and Gunn assures her that he loves her as a friend. Edie isn't convinced but jokingly puts it off and suggests that she might pay him for some of his time. When she asks what he's doing that night, Gunn says that he has to run an errand for Mother as Edie's piano player, Emmett Ward, calls her in for her next number.
Gunn tracks Fallon down to the Elite Health Club where the mobster spends his time off. Two gunmen stop Gunn at the door but he quickly takes offense and starts a fight. They go for their guns and Gunn draws his weapon, but Green comes in and calls them off. Green then escorts Gunn to the racquetball court where Fallon is busy defeating his opponent. Once he finishes, Gunn tells him to lay off Mother but Fallon tells the detective to pick better friends and walks away.
On his way back to Mother's, Jacoby picks Gunn up and they discuss Fusary's murder. The lieutenant figures that Fusary used a fake police car and uniforms to pull off the high-profile murders, but admits that he doesn't have any evidence to prove it. Gunn tells him to check back when he has some and goes into the club, where Edie and Emmett are rehearsing. Mother approaches the detective and tells him that Fallon's men already called demanding their protection money, but she's not going to pay. Edie invites Gunn out for a late dinner and the two of them go to the back to get their coats. As they do, Mother hears something moving beneath the floorboards and calls over Barney the bartender. As Gunn and Edie leave, an explosion rocks the club and they run back inside to find a badly injured Mother.
Later, Green leaves the health club and Gunn picks him up at gunpoint and forces him to drive to the club. He tells the mobster that if the hospital calls with news that Mother is dead, he'll put a bullet in Green's head. The panicky Green sits on the floor and they wait until Edie calls. She tells Gunn that Mother pulled through, but he doesn't tell Green that and hangs up right away. When he prepares to shoot, Green cracks and tells him that Fallon hired a tailor to make the uniforms and then had the man killed and dumped in the river. Satisfied, Gunn tells him to call Fallon and demand $50,000 for his silence, and to bring the money to the club. Green warns him that Fallon will simply send his men to kill them, but Gunn persists and Green reluctantly makes the call.
Fallon sends his two gunmen in the fake uniforms, driving the fake police car, to knock off Green. Gunn turns off the lights and prepares to capture them, but Edie comes in unexpectedly, alerting the gunmen. Green hits Gunn with a bottle and runs outside, claiming he was forced to call them, and the gunmen shoot him down. Jacoby arrives and the fake cops drive off, only to run into a waiting roadblock. They try to shoot their way out but Jacoby and his men easily shoot them down. Inside the club, Gunn nurses his injured head and Edie admits that when he hung up on her, she got nervous and called Jacoby.
Fallon sends his two men in their fake police car, just as Peter expected. Peter turns off the lights just as Edie comes in unexpectedly. Green hits Peter with a bottle and runs out, but the two gunmen shoot him down. Jacoby arrives and chases them into a roadblock where they're gunned down. Inside, Edie explains that when Peter hung up, she got nervous and called Jacoby.
Later, Jacoby finds the tailor's corpse and pins the murder to Fallon. Mother is soon out of the hospital and has the club back in business with Edie performing.