Robert "Fish" Fishman (Rainn Wilson) and a trio of his Cleveland buddies create a headbanging, Spinal Tap-esque band known as Vesuvius in the eighties. They are living the rock 'n' roll dream and seem on the road to fame and fortune. But if the band wants to take the next big step to a record contact they have to dump their sweaty overweight drummer Fish. It takes them about ten seconds to make their decision.