Millie can't wait to celebrate "Galentine's Day" with her friends at Chestnut Academy! But when her father asks her to spend the day with her kid brother, Willie, Millie fears that she'll break the most important club rule: No Boys Allowed! Meanwhile, the boys at Craven Hall have a surprise of their own up their sleeves. They challenge the young ladies of Chestnut Academy to go head-to-head in an exciting competition! But the invitation comes with a twist: they must attend the Craven Hall school dance!  Will Millie and her friends defeat the boys? Or will they be forced to surrender in the middle of their prank war? Ride and laugh along with Millie and the M&M gang in a brand-new adventure!