Hating being pushed around and unappreciated by predators throughout her whole life, she organizes a plan to turn prey species against the predator minority of Zootopia. To do so, she tasks her subordinate Doug (a sheep chemist and sniper), to extract the essence of Nighthowler plants (which can turn prey and predators savage) into pellets, and to shoot predator citizens, thus causing mistrust and paranoia throughout the city.

Though her plans were temporarily stalled due to Mayor Lionheart's intervention by imprisoning the savage predators in a secluded building until a cure could be found. Through her manipulations, she guides Judy and Nick to the building containing the imprisoned predators, allowing the duo to obtain evidence which results in Lionheart's arrest. She then becomes Mayor of Zootopia.

During the Climax where she reveals herself as the villain, she shoots Nick with a Nighthowler pellet and calls the ZPD so that they can witness the death of Judy in the hands the savage Nick. But it is revealed that Nick was just pretending, and Judy had secretly recorded Bellwether admitting her crimes. She is swiftly arrested after the ZPD arrive and sent to prison.