A Valentine's Day dance at Greg's middle school has turned his world upside down until an unexpected twist gives Greg a partner for the dance and leaves his best friend Rowley the odd man out.
When snow closes Greg Heffley's middle school, he and his best friend, Rowley Jefferson, face a fight for survival as warring gangs turn the neighborhood into a wintry battlefield.
Tagging along with his brother Rodrick's band, Löded Diper, Greg gets more than he bargained for when he gets a backstage pass to the rock 'n' roll lifestyle and wonders if he can help them become the legends they think they are.