After stepson Trent witnesses a murder, FBI agent Malcolm Turner brings back Big Momma, his plus-size alter ego, to help solve the crime. Big Momma goes under cover at a girls school of the performing arts, but this time he has Trent and Trent's female alter ego Charmaine as backup. The duo must try to find the killer before the killer finds them, but complicating matters is Trent's crush on a student.