The O'Leary brothers--honest Jack and roguish Dion--become powerful figures, and eventually rivals, in Chicago on the eve of its Great Fire.

In 1854, Patrick O'Leary, patriarch of the O'Leary family, dies in an accident nearby Chicago while traveling the Midwestern prairie. His wife Molly O'Leary raises her three sons alone, working as laundress. Her son Jack becomes an idealistic lawyer, Dion is a gambler, and Bob helps his mother in the laundry business and marries local Gretchen (June Storey) in the old area known as The Patch. Dion meets singer Belle Fawcett in the cabaret owned by Gil Warren and they fall in love with each other. They also open their own business to compete with Gil, who becomes their enemy. However, Gil invites Dion to join politics with him but Dion plots a scheme with tragic consequences.—Claudio Carvalho, Rio de Janeiro, Brazil