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.

While driving through the New Mexico Desert during a rainy night, college students Jim Halsey and his girlfriend Grace Andrews give a ride to a hitchhiker. While in their car, the stranger proves to be a psychopath threatening the young couple with a knife, but Jim successfully throws him out of the car. This sets off a chain of events that will change all of their lives forever.