Attorney James Markey has grown rich defending mob kingpin Louis Joe and his minions. His wife, Iris, is disgusted by the source of their lavish lifestyle and walks out on him when he refuses to quit. Markey goes into a alcoholic tailspin and winds up penniless, living on the mean streets of the Lower East Side. He meets a young street urchin, Chubby Dennis, who teaches him how to survive life in the slums. Their new friendship gives James a reason to go on living. Caught in the middle of a gangland battle, little Chubby is struck and killed in a hail of bullets. Saddened and enraged, James Markey vows to get his life back in order and offer himself to the D.A., determined to devote his future to bringing the killers to justice.
Beginning at the age of seven, Mickey Rooney starred in 78 "Mickey McGuire" comedies, starting in 1927 with Mickey's Circus, and continuing to 1936. In 1937, the same year he starred in Hoosier Schoolboy, he would appear in A Family Affair as Andy Hardy, the first of 14 films in the wildly successful series that would run until 1946. Although 12 years of age when Slums Of New York was filmed, he could easily pass for a seven-year-old.