Maggie Johnson, or Mag, is a child of the tenements in the Bowery, a place of extreme poverty, deprivation, and—for Mag—child abuse. As she matures from "a small ragged girl" to a pretty young woman, the Bowery men begin to notice her. Maggie is only interested in Pete and feels protected by his tough talk and swagger. She trusts him to give her the better life she craves. When their relationship becomes physical and Maggie stays away from home, her mother and brother reject her. She tries to return home when Pete runs off with Nellie, but she is shunned by her family and neighbors. Homeless, jobless, and friendless, Maggie survives on the streets as a prostitute until her death.
Jimmie Johnson is "the little champion of Rum Alley," defending his turf from a neighboring gang. His father beats him to break up the fight, and his mother beats him for wrecking his clothes. Jimmie grows up to be a truck driver, frequently fighting for right of way, or getting dragged off and beaten by cops. His daily routine mimics those of his parents: stumbling home to sleep off a drinking binge. Jimmie harshly judges Maggie for having sex with Pete. Jimmie has a vague sense it is wrong for a friend to ruin one's sister, so he goads Pete into a fight. He also considers the possibility the women with whom he has sex might have brothers but does not see the hypocrisy of his condemnation of Maggie. When Hattie finds him, perhaps to ask for support for a baby, Jimmie tells her to "go teh hell," just as Pete does to Maggie.
Pete is an older kid in the neighborhood who intervenes in little Jimmie's turf battle. As they get older the boys enjoy bragging about their fighting abilities. Pete is visiting Jimmie when he notices Maggie and soon begins taking her to shows and clubs. After their relationship becomes sexual and Maggie stays away from home, Pete abandons her at a show and leaves with Nellie. Now homeless, Maggie tracks down Pete at work to ask for help, but he tells her to "go teh hell." Perhaps knowing Maggie has turned to prostitution, Pete tries to appease his conscience by drunkenly overspending on cocktails for Nellie and a group of women who tell him he is good. He tells Nellie he is "stuck on" her and, when he passes out, she takes his money and calls him a "damn fool."
Mary Johnson, "the mother," beats her children for ruining their clothes or breaking a dish and battles with her husband. As the years go by her alcoholism and rage increases. The mother is utterly astonished when "Maggie's gone teh deh devil," believing she had given her a good upbringing. Jimmie suggests Maggie could come home so they can all avoid the public shame, but the mother will not hear of it. She relishes the idea Maggie will be unhappy and long to come home one day. When the day comes, the mother and Jimmie reject Maggie. The mother laughs, and the neighbors jeer. When she learns Maggie is dead, the mother can only think of the little knitted baby booties Maggie once wore. A mourner comes and presses the mother to forgive Maggie, and she finally does.