After he is fired from the Anti-Villain League for failing to take down Balthazar Bratt, the latest bad guy to threaten humanity, Gru finds himself in the midst of a major identity crisis. But when a mysterious stranger shows up to inform Gru that he has a long-lost twin brother - a brother who desperately wishes to follow in his twin's despicable footsteps - one former super-villain will rediscover just how good it feels to be bad.