For Tammy (Melissa McCarthy), a burger-joint waitress, a bad day keeps getting worse. She wrecks her car, loses her job and finds her husband in a compromising position with their neighbor. It's time for Tammy to hit the road, but without money or transportation, her options are limited. Her only choice is a road trip with her grandmother, Pearl (Susan Sarandon), who has a car, cash and an itch to see Niagara Falls. It's not the escape Tammy had in mind, but it may be what she needs.