Tells the story of one day in the lives of the various people who populate a police detective squad. An embittered cop, Det. Jim McLeod, leads a precinct of characters in their grim daily battle with the city's lowlife. The characters who pass through the precinct over the course of the day include a young petty embezzler, a pair of burglars, and a naive shoplifter.
Mobster "Baby Face" Martin returns home to visit the New York neighborhood where he grew up, dropping in on his mother, who rejects him because of his gangster lifestyle, and his old girlfriend, Francey, now a syphilitic prostitute. Martin also crosses paths with Dave, a childhood friend struggling to make it as an architect, and the Dead End Kids, a gang of young boys roaming the streets of the city's East Side slums.
A dedicated young doctor places his patients above everyone else in his life. Unfortunately, his social register fianceé can't accept the fact that he considers an appointment in the operating room more important than attending a cocktail party. He soon drifts into an affair with a pretty nurse who shares his passion for healing.
