Margaret and Susan Turner are two sisters sharing a home, bound by their unique personalities. The 17-year-old Susan is an exceptionally bright high school student, known for her fleeting passions, often inspired by the guest lectures at her school. Margaret, a judge, assumes the role of guardian to her younger sister.

The narrative takes an intriguing turn when Richard Nugent, a charming artist played by Cary Grant, finds himself in Margaret’s courtroom. He faces charges from assistant district attorney Tommy Chamberlain, portrayed by Ray Collins, for allegedly inciting a brawl at a nightclub. However, when it becomes apparent that the altercation stemmed from two women competing for Richard’s attention, Margaret admonishes him but ultimately releases him.

Later, Richard visits Susan’s school as a guest speaker, and it’s there that Susan becomes irresistibly drawn to him. Captivated by his charm, she expresses a desire to model for him, leading to a daring escape from home later that night. Dressed elegantly for the occasion, she sneaks into Richard’s apartment while he is out.

Upon Richard’s return, chaos ensues as Tommy and Margaret confront them, leading to a physical altercation between Richard and Tommy. To defuse the situation, their uncle, Matt Beemish—also the court psychiatrist—intervenes. He suggests allowing Susan to date the much older Richard until her infatuation fades, and Tommy agrees to dismiss the assault charges if Richard complies.

At a high school basketball game, Richard attempts to aid Susan’s reputation concerning her ex-boyfriend, Jerry White. During a school picnic, Susan convinces Richard to participate in various novelty races, yet Richard struggles against Tommy, who triumphs repeatedly. In a climactic performance during an obstacle course event, Susan persuades Jerry to assist Richard, primarily because Jerry still harbors feelings for her. He strategically sabotages the other competitors, allowing Richard to secure victory.

Amid the humorous predicaments, Richard and Margaret are clearly drawn to one another, but Tommy, viewing Richard as a perpetual troublemaker, lays claim to Margaret. To alleviate the tension, Tommy proclaims that he is dropping charges against Richard, hoping this will discourage Margaret’s burgeoning affections for him. As Richard and Margaret attempt a night out at a nightclub, their evening is disrupted for comedic effect. In a moment of drama, Susan accuses Margaret of hijacking her new boyfriend, prompting Uncle Matt to step in. He gently helps Susan realize that her feelings for Richard are merely infatuation and encourages her to reconnect with Jerry, who is preparing to go off to the military.

In a twist of fate, Matt devises a plan when he learns about Richard’s plans to leave town. He convinces Margaret that a getaway is exactly what she needs, booking her on the same flight as Richard. When Tommy arrives at the airport to wrongfully apprehend Richard, Matt cleverly misleads the authorities into believing Tommy is a delusional mental patient. Eventually, Richard and Margaret find themselves pleasantly surprised to meet at the airport, ready to embark on their new journey together.