The film is largely set in ZEN, a bleak, economically deprived quarter on the northern outskirts of Palermo, Sicily, at the end of the 1980s.

Its protagonist is Natale Sperandeo (played by Palermo-born actor Francesco Benigno), a young man who has just been released from Malaspina, a juvenile detention centre.

The film also traces the divergent paths taken by his former inmates at Rosaspina (actual name Malaspina), such as Marilyn "Mery" Libassi, who resumes her previous career as a trans prostitute while awaiting trial for her self defense assault on a client; Claudio Catalano, while seeking to avoid the vindictive Carmelo Vella (who blames Claudio for the loss of his left eye), obtains work as a mechanic in another neighbourhood, but shortly afterwards discovers his girlfriend, Vita is pregnant; Antonino Patané is forced to push drugs in order to maintain his two small children after the financial police sequester his potatoes which Antonino was selling without a license; and Giovanni Trapani, nicknamed King Kong and a member of Natale's gang, is fatally shot by a plainclothes police officer outside the open-air market of Vucciria after a long chase through the streets of Palermo for having robbed a car radio.

Boys on the Outside accurately depicts the social problems faced by Natale and his companions, such as crime, poverty, unemployment, prostitution, teenage pregnancy, and police harassment, which were indelible features of life in the poorer districts of Palermo and other Sicilian cities during that time period.

Francesco Benigno won two awards, the Ciak d'Oro at the Venice Film Festival, and Premio Piper, for Best Actor in his portrayal of Natale Sperandeo.