Taking place right after the events of its predecessor, The Incredibles features the Parr family alongside Lucius Best, also known as Frozone, as they engage in a fierce battle against the Underminer. Although they manage to thwart the villain's attempt to demolish city hall, their efforts fall short when he escapes after robbing a bank. The aftermath of this lukewarm victory and the considerable destruction incurred leads the government to terminate the Superhero Relocation Program, which previously provided financial support for the heroes. In a twist of fate, Violet's classmate and crush, Tony Rydinger, inadvertently uncovers her superhero secret. Meanwhile, Agent Rick Dicker mistakenly wipes Tony's knowledge of Violet entirely, intensifying the stakes.
Wealthy siblings Winston and Evelyn Deavor, founders of the telecommunications company DevTech, propose covert missions to Helen (alias Elastigirl), Bob (alias Mr. Incredible), and Lucius, aimed at restoring public confidence in superheroes through recorded broadcasts. Winston opts for Helen to be the face of these initial missions, given her relatively minor record of property damage. Initially hesitant to leave her family and the risk of legal repercussions, Helen ultimately agrees after a heartfelt conversation with Bob. To facilitate their work, Winston relocates the Parrs into an opulent mansion.
As the action unfolds, Bob grapples with his new responsibilities as a stay-at-home dad. He's left managing Violet's feelings of disappointment over Tony's amnesia, assisting Dash with his challenging math homework, and navigating the growing chaos caused by baby Jack-Jack's emerging powers. Amidst these trials, Bob fights feelings of envy towards Helen and, guided by Lucius, enlists the help of Edna Mode to babysit Jack-Jack.
In the bustling metropolis of New Urbem, Helen faces off against the sinister Screenslaver, a crafty hacker who employs hypnosis via screens to manipulate others. After averting a catastrophic hovertrain disaster and foiling an assassination attempt on an ambassador, she traces the villain's signals back to his lair. In a dramatic confrontation, Helen defeats Screenslaver, only to unmask a confused pizza delivery driver, who is perplexed by his predicament. During a party celebrating her victories, Winston announces an upcoming summit of world leaders aboard his luxurious hydrofoil yacht, the Everjust, intended to legalize the "supers."
However, the plot thickens as Helen discovers that Screenslaver has led her into a well-laid trap. The deceived pizza deliverer falls prey to hypnotic devices, and Evelyn ultimately unveils her true identity as Screenslaver. She captures Helen, utilizing her goggles and a freeze cell that negates her powers, expressing bitterness over society's reliance on superheroes, which she believes contributed to the demise of their parents; their father was shot by intruders when help was needed from the now-outlawed heroes, Fironic and Gazerbeam, while their mother succumbed to grief. Evelyn's plan is to ruin the reputation of all "supers" internationally, hoping that a world free of crime-fighting heroes would be safer.
Evelyn lures Bob into a clearly set trap aboard the Everjust, where he falls under her control, sending a wave of mind-controlled supers to overpower Violet and Dash. Lucius intervenes to defend them but finds himself goggled as well. Seizing the opportunity, they manage to escape with Jack-Jack in the Incredibile, their father's refurbished supercar. Intuitively aware of their parents' plight, they stow away on the Everjust and swiftly find themselves in a precarious situation where Helen, Bob, and Lucius must broadcast villainous lines, incapacitating the crew and locking the ship on a collision course back to New Urbem.
Just as disaster looms, the children arrive in the nick of time; Jack-Jack removes Helen's goggles, allowing her to free Bob and Lucius. Joined together, they succeed in liberating the remaining controlled supers, skillfully steering the Everjust into safe harbor. Although Evelyn manages to escape via the yacht's parasite jet, she is swiftly apprehended by Helen.
With yet another crisis averted, public perception of "supers" shifts positively, achieving Winston's long-desired outcome. In a heartwarming denouement, some time later, Violet picks up Tony in the Incredibile for their long-awaited movie date. As they head to the cinema, the family spots a police chase in progress; Violet leaves Tony with a promise to return shortly before the Parrs excitedly don their superhero masks, ready to jump back into action.
