Louie Ricarno, un jeune chef de gang à Chicago, devient le patron des bas-fonds de la ville. Il tombe amoureux de Doris, sans savoir qu'elle est en fait avec son second, Steve Mileaway. Lorsque Doris accepte de l'épouser, Louie décide de tout quitter et de partir pour la Floride. En chemin vers le sud, il s'arrange pour que Doris rencontre son jeune frère Jackie, qui est dans une école militaire sous un faux nom. Une fois en Floride, Doris s'ennuie, Chicago lui manque. Pendant ce temps, Mileaway est incapable de mettre fin à une guerre des gangs qui s'est déclenchée à Chicago, il demande à Louie de rentrer pour reprendre les choses en main, mais ce dernier refuse. Pour le forcer à revenir, il décide de faire kidnapper Jackie. Hélas, comme il est approché par deux hommes de main, Jackie sent un danger et s'enfuit, mais il est renversé par un camion. Louie revient alors à Chicago pour se venger. Malgré les conseils du chef de la police O'Grady, il tue les coupables, mais est obligé de se cacher. Après quelque temps, il décide de sortir fièrement de sa cachette, sachant très bien que ses ennemis l'attendent dehors.
Monte Blue plays as a police detective who is after a famous gangster (played by William Boyd). He disguises himself and lives in the very house of the famous gangster by pretending he is an out-of-town gangster who has just murdered someone. He pretends he is the sweetheart of an innocent girl (played by Lila Lee) who suspects her brother has been framed for murder by Monte Blue. Blue's moll, played by Betty Compson, is also in on the conspiracy as she had become fed up with his cheating, lying and brutal treatment. The life of Lee's brother depends, who has been sentenced to death in the electric chair, depends on them getting evidence against Boyd.
Jean Oliver (Claudette Colbert) sort de prison après avoir été accusée à tort de vol par une vieille dame. Elle rencontre The Fox (Edward G. Robinson), leader d'une bande de voleurs de bijoux se cachant derrière un cabinet de voyance pour mener leur délits. À la suite d'un accident de train, la femme faisant office de voyante au sein de la bande, Madame Mysteria, meurt. Jean Oliver prend alors sa place, mais demande en échange de kidnapper la petite-fille de l'accusatrice pour se venger de la responsable de ses années passées en prison.
Jerry Larrabee (Richard Barthelmess) is framed by rival gangster Spadoni (Louis Natheaux) and sent to prison, where he is befriended by a kind and understanding warden (William Holden). Through the warden's patient influence, Jerry becomes interested in music and forms a prison band, broadcasting over the radio. Jerry's singing deeply moves his radio listeners and soon Jerry is given a pardon by the governor.
The film focuses on the 'Plain Clothes Men', a group of detectives dressed up as average citizens to catch criminals without being noticed. They are especially hated by the underworld due to their constant meeting, during which suspects are analyzed and interrogated extensively. Among the staff is Dan Coghlan (Lon Chaney), a police officer with flat feet and a tough disposition, who is unsatisfied with the lack of adventure. As he is about to quit his job, he is noticed about a croaked jeweler. When arriving there, he finds Skeeter Carlson (Wheeler Oakman), a crook who never gets busted for a crime due to a lack of evidence.
The film follows the saxophone player Clyde, who busks on the San Francisco Bay waterfront. One night, he meets Flowers, and teaches her to dance, but finds that "Blackjack" (Eddie Gribbon), the leader of a ruthless gang, is also in love with her. Despite the intense turf war between "Blackjack" and a rival gangster named Mike Luego (Walter Long), "Blackjack" wins the heart of Flowers and marries her, but without consummating the marriage. Clyde is eventually able to win "Blackjack" over however, and "Blackjack" sacrifices himself to protect Clyde and Flowers from Luego. Gang War was produced in black and white on Academy ratio 35 mm film, and was originally to be a silent film. However, a spoken prologue was added, in which a group of reporters (including one played by Mabel Albertson) discuss the events that are to come.
The gang of a mob boss get suspicious his new girlfriend. Because she's a beautiful young girl they don't believe she would actually associate with the mob and wonder if she's really a police "plant". The mobsters dress nattily to not appear "out of place" in the ritzy neighborhoods prior to a heist.
Jimmy Williams vole 50 000 $, mais il est arrêté avant d'avoir pu les dépenser. Il est condamné et envoyé en prison. Il y change de comportement à la suite de la mort de sa mère et grâce à l'influence de Mary Regan. Libéré sur parole pour bonne conduite, il décide d'aller dans le droit chemin et de rendre son butin. Les anciens membres de son gang, en apprenant cela, vont chercher à lui reprendre l'argent. Mais, avec l'aide de Mary, Jimmy parviendra à les devancer. Il pourra alors repartir pour une nouvelle vie avec Mary.
Bull Weed, un des chefs de la pègre à Chicago, a pris sous sa protection un ancien avocat ruiné par l'alcool, véritable épave surnommée Rolls Royce. Celui-ci est amoureux de Lucy, la compagne de Bull.