Inspired by a car race in the distance, Phineas and Ferb upgrade Mom's car and turn it into race car 42, and enter it in the Swamp Oil 500 where Phineas races against other racers with Ferb acting as his helper and Isabella and the Fireside Girls as his pit crew. Candace constantly tries to bust them by just surprising Linda with what they're doing, but keeps missing by just a second. Elsewhere, Dr. Doofenshmirtz tries to deflate everything in the Tri-State Area from his blimp.