In search for a woman, Will (Hugh Grant), a rich, child-free and irresponsible Londoner in his thirties, invents an imaginary son and starts attending single parent meetings. As a result of one of his liaisons, he meets Marcus, an odd 12-year-old boy with problems at school. Gradually, Will and Marcus become friends, and as Will teaches Marcus how to be a cool kid, Marcus helps Will to finally grow up.