Promptly after being the recipient of a gangster rendition of "For He's a Jolly Good Fellow," mafioso Big Jim is gunned down at his birthday party. Immediately Guy Gisborne (Peter Faulk) claims new reign of Jim's territory. Robbo (Frank Sinatra) quickly warns Guy to keep his nose out of Chicago's north side, but the two gangsters are by no means cooperative. Amidst gang wars and police raids, Big Jim's daughter Marian (Barbara Rush) offers Robbo $50,000 to avenge her father's death. Though the culprit is no longer living, Marian sends Robbo the cash anyway. Robbo orders his goon Will (Sammy Davis, Jr.) to dispose of the money. Will offers the sum to the Blessed Shelter Orphans Home run by Allen A. Dale (Bing Crosby)--in Robbo's name. Delighted, Father Dale informs the Chicago press and soon Robbo is regarded as the modern-day Robin Hood. Robbo soon begins to fall for Marian, but eventually learns that she, too, knows how to play the criminal game--and with, of all people, Robbo's pal John (Dean Martin). With such a cast of famous songsters, Robin and the Seven Hoods is full of musical performances including the popular tune at the time, "Style," sung by Martin, Crosby and Sinatra. Nelson Riddle contributes his musical abilities, as well.