Will Freeman is a good-looking, smooth-talking bachelor whose primary goal in life is avoiding any kind of responsibility. But when he invents an imaginary son in order to meet attractive single moms, Will gets a hilarious lesson about life from a bright, but hopelessly geeky 12-year-old named Marcus. Now, as Will struggles to teach Marcus the art of being cool, Marcus teaches Will that you're never too old to grow up. Will, who attends single parent meetings to woo women, meets Marcus, a troubled 12-year-old boy. As they become friends, Will learns to be responsible while he helps Marcus with his studies.