The story follows Nick Twisp, a unique, wise-beyond-his-years teenager with a taste for the finer things in life like Frank Sinatra and avant-garde cinema. Living with his divorced mother and her boyfriend in Oakland, California, Nick's life is far from his sophisticated fantasies. His mother’s choices in men usually lead to transient, bleak housing situations and a deep dissatisfaction for Nick about his place in the world. Craving change and an escape from his mundane existence, his life takes an unexpected turn when during a family trip, he meets Sheeni Saunders, an intelligent and free-spirited girl who shares his interests and dreams.

Immediately smitten, Nick finds himself desperate to win Sheeni's heart, but there's a significant obstacle—she has a boyfriend. Inspired by Sheeni's adventurous spirit and his own desperation to shed his dull life, Nick conjures up an audacious plan. He develops an unruly alter ego named François Dillinger: a mustachioed, cigarette-smoking rebel without a care in the world. The suave and Gallic François is everything Nick isn't, and he gives Nick the confidence to pursue Sheeni and upend his life in an effort to impress her. Nick's actions, under the influence of his brash doppelgänger, set off a chain of events filled with humor and anarchy, which not only threaten to ruin his chances with Sheeni but also turn his entire life upside down.