They both live with their grandmother, who is an avid supporter of Alderman Marvin Harris, a politician from their neighborhood running for mayor on an anti-corruption platform.

Darryl is overly optimistic and almost childishly naive to the harsh realities of living in the inner city (such as the crackhouse next door), but is a brilliant inventor, having constructed a mobile robot assistant named J-5, among other creations.

The murder opens Darryl's eyes to the urban decay around him and he begins to fight crime by boldly saving an elderly transit passenger from being mugged, but overreaches by storming the crackhouse next door to rebuke the gang members.

He then decides to become a vigilante superhero, using his technical expertise to create weapons and gadgets – in particular, a substance which renders ordinary clothing bulletproof – for his crime-fighting crusade, all to the annoyance of Kevin.

Kevin changes his mind and goes along with the fantasy, believing that it's Darryl's way to cope with the murder of their grandmother, but under the guidance of starting a neighborhood watch instead.

Over time, Darryl uses his Blankman identity to protect various community members, build up a reputation, and inspire not only the town's citizens but other real-life superheroes.

Mayor Harris attempts to bring in outside money to pay the IOUs the city has been giving its workers and requests that Blankman be there to protect the people and receive a special award.

As the money is released, Minelli's henchmen storm the bank and take the mayor hostage, threatening to detonate explosives.

At the police chief's request and the crowd's chants, Blankman attempts to save the mayor, but even with Kevin's help, he is unable to stop the crooks, nor defuse the bombs.

Wanting a great story, Larry Stone manages to contact Minelli and trades knowledge of Blankman's love for Kimberly in exchange for an exclusive interview.

The duo then finds the bombs in the women's bathroom, and stuffs the explosives inside J-5, while he frees Kimberly (Stone is left behind, as a joke by Other Guy).

[7] One critic who gave it a mildly positive review was Stephen Holden of The New York Times, who said that it "gets most of its comic mileage from its wonderful gadgets and from Mr. Wayans's sweetly myopic performance" and that the film "plays it light and silly but not so broadly that the movie collapses into chaos.