When he is summoned to jury duty, Throckmorton P. Gildersleeve regards his responsibiltiy as an honor. Gildy and fellow jurors druggist J. W. Peavy and Otis, a newlywed, are assigned to the trial of an accused bank robber named Louie. To make sure that their boss wins acquittal, Toad and Al, two members of Louie's gang, decide to bribe a juror and choose Gildy as their victim. Drafting a letter signed "anonymous," the crooks offer Gildy $1,000 if he will vote to acquit Louie. The letter gets sidetracked by Gildy's niece, Margie Forrester, who slips the unopened envelope in his coat, which is then picked up by George Peabody, the busy-body dry cleaner. Fancying himself a legal expert, Gildy holds out for Louie's acquittal despite overwhelming evidence of guilt. When George returns the letter to Margie and mentions that the jury is deadlocked, she thinks that her uncle accepted the bribe. Accompanied by her little brother Leroy, Margie rushes to the courthouse to confer with her uncle. Informed by Judge Horace Hooker that the jury is to be sequestered, Margie invites them all to spend the night at the Gildersleeve house. Margie and Leroy's attempts to speak to their uncle are thwarted, however, by the zealous bailiff, who refuses to let them see Gildy. Meanwhile, George visits the house and threatens to disclose the contents of the letter unless Margie agrees to attend the dance with him. To protect her uncle, Margie stands her boyfriend Jimmy up and accepts George's invitation. That night, as Jimmy and George fight over Margie at the dance, Gildy browbeats his fellow jurors into acquitting Louie. Although furious at the jury's decision, Judge Hooker is forced to release Louie. Upon learning that his gang promised Gildy $1,000, Louie insists upon paying the bribe and steals the money from the judge's safe. The next morning, when a messenger presents Gildy with an envelope filled with cash, he thinks that the money is a donation from Mrs. Hastings to the canteen fund. At Peavy's drugstore, the druggist tells Gildy about the robbery and adds that the judge posseses a list of serial numbers from the stolen bills. After paying for his coffee with one of the bills from the envelope, Gildy visits the judge to deliver Mrs. Hastings' donation, which the judge then locks in his new safe. After Gildy returns home, Margie and Aunt Emma, who has come to visit, show him the gangsters' letter, and he realizes that the money did not come from Mrs. Hastings, but was stolen from the judge's safe. Determined to recover the bills before the judge discovers the source of the money, Gildy sneaks into the Hooker house that night. He is preceeded by Louie and his gang, who have rigged the safe with explosives. As Gildy approaches the safe, it explodes, blowing off his pants and awakening the judge. After grabbing the cash from the safe, Gildy takes refuge in the back of a police car, but when the car's occupants are summoned to the judge's house to investigate the robbery, Gildy jumps out of the car and dodges behind some bushes. Trailed by police bloodhounds, Gildy discards his clothes and runs home, and when the police find the clothes, they put the Gildersleeve house under surveillance. Also watching the house are the robbers, who want their loot. After hastily dressing, Gildy leaves the house and is kidnapped by the robbers, who hijack a police car and force him to drive them into the countryside, where they plan to kill him. Unknown to the crooks, Gildy switches on the police radio and broadcasts their conversation. When the gangsters realize what is happening, Gildy crashes the car into a lamp post. Upon awakening in the hospital, Gildy claims that the whole episode was part of his grand scheme to round up the mob.