Helen and Ken are a pretty strange couple. She is a pathological liar, and he is a scrupulously honest (and therefore unsuccessful) lawyer. Helen starts a new job, and when her employer is found dead, all the (circumstantial) evidence points at her. She is put on trial for murder, and her husband defends her. He thinks she is lying again when she says she didn't do it, and insists she plead that she did, but in self defense. Charlie, a shady, odd character who may or may not know something about what really happened, hangs around the courtroom and jail making rude comments and noises. After Helen is acquitted, he tries to blackmail them.

Helen Bartlett, fiction writer and chronic teller of fibs, is happily married to honest lawyer Ken, but they are broke. Helen secretly gets a job as a secretary, but quits her first morning when her boss, Otto Krayler, proves to be a lecherous wolf. When she returns later for her hat and coat, Helen is charged with murder. The apparent motive for the crime is $12,000, which strangely was left in Krayler's desk. When Helen is cross-examined, she paints a vivid scenario of her guilt, then says she is innocent. Ken visits Helen in her jail cell and, fearing there is no way to prove her innocence, decides to plead self-defense, hoping to win the jury's sympathy for a woman protecting her honor. Throughout the trial, all assume Helen is guilty except a mysterious man named Charley Jasper, who calls himself a criminologist and "student of life." The Bartletts win the case after much publicity, and Helen publishes her life story, becoming a wealthy novelist. At their new home on Martha's Lake, Ken feels guilty that crime catapulted them to success, and Helen is ready to confess her innocence when Ken states categorically perjury is a travesty of justice worse than murder. Charley visits the Bartletts carrying Krayler's wallet, and hopes to blackmail them with knowledge of Helen's perjury by confessing to the murder himself. Helen finally tells Ken the truth, and he threatens to turn Charley in until he confesses the real murderer was his brother-in-law, who panicked after killing Krayler and abandoned the money, then was himself killed during an attempted bank robbery. Ken, disillusioned by Helen's constant lying, leaves, but she runs after him, lying that she's pregnant, then insisting it could be true. Ken then carries Helen into the house in order to make one last attempt to teach her not to lie, and she assures him she has uttered her last fib.