The Dead End Kids are introduced in their intricate East Side slum, overlooked by the apartments of the rich. Their antics, some funny, some vicious, alternate with subplots: unemployed architect Dave is torn between Drina, sweet but equally poor, and Kay, a rich man's mistress; gangster Baby Face Martin returns to his old neighborhood and finds that nobody is glad to see him. Then violent crime, both juvenile and adult, impacts the neighborhood and its people.

It is a normal day for everyone, until President of the United States James Dale (Jack Nicholson) announces Martians have been spotted circling Earth. The Martians land and a meeting is arranged, but not everything goes to plan, and the Martians seem to have other plans for Earth. Are they just misunderstood beings or do they really want to destroy all of humanity?