Elizabeth "Lizzie" Cronin, a shy and repressed woman, finds her life in disarray. Her marriage is failing, her car is stolen, and she loses her job. Forced to move back in with her controlling mother, Polly, Lizzie's childhood is revisited when she discovers a long-forgotten jack-in-the-box. The box contains Drop Dead Fred, an unruly and chaotic imaginary friend who once wreaked havoc during her youth. Fred returns, visible only to Lizzie, intent on helping her regain her confidence by creating more chaos. Fred’s antics cause Lizzie further embarrassment at every turn, making her question whether having him around is really helpful.

Despite the turmoil, Fred’s unorthodox methods lead Lizzie toward self-reflection, as she begins to understand how much of her spirit was suppressed by her strict upbringing. As Fred causes mayhem wherever they go, Lizzie starts piecing together her past and confronting the issues in her adulthood. She struggles with reconciling Fred's influence with her desire for a stable life. The journey deepens as Lizzie grapples with maintaining her sanity amid Fred's unrelenting presence while trying to mend the relationships and reevaluate what really matters to her. This unexpected self-exploration challenges Lizzie to break free from the constraints of her upbringing and find her true self amid the chaos wrought by Fred.