Tammy (McCarthy) is having a bad day. She's totaled her clunker car, gotten fired from her thankless job at a greasy burger joint, and instead of finding comfort at home, finds her husband getting comfortable with the neighbor in her own house. It's time to take her boom box and book it. The bad news is she's broke and without wheels. The worse news is her grandma, Pearl (Sarandon), is her only option with a car, cash, and an itch to see Niagara Falls. Not exactly the escape Tammy had in mind. But on the road, with grandma riding shot gun, it may be just what Tammy needs.