Due to the prison needing room for the truly dangerous criminals (like constant cell-phone talkers and people who tape sporting events without written consent), Sideshow Bob is released and he anticipates his murder of Bart Simpson... then is hit by a bus. Though Bob survives, Bart reads in the paper that plastic surgeons had to reconstruct his face due to the injuries sustained, and he realizes that Bob could now look like anyone.
With help from Lisa, Bart is given the identities of the three people who most likely would be Bob. The first two suspects are proven to not be Bob due to them lacking his trademark cultural taste. When Bart investigates the third suspect, he slips and falls into the suspect's yard, where a pair of large poodles are kept. The first poodle suddenly pulls off his head, revealing himself as Sideshow Bob (and that the face-surgery was purely for touch-ups, as he looks no different from before). Bart is saved when the second poodle is revealed to be Sideshow Mel, who anticipated his predecessor's plans and was keeping a close watch on him. His plan foiled again, Bob is sent back to prison, where he rots in a cell with the phone-talkers and sports-tapers.