Four criminals murder a night watchman while robbing a warehouse. After kidnaping the daughter of their victim they hide. One of the robbers falls for their hostage, leading to tension between the thieves.
Scott (Ron Foster) is a frustrated police detective constantly being passed over for promotion. When he's assigned to gain the confidence of Holly (Patricia Blair), the girlfriend of a suspect in a robbery, the couple fall in love, plot to murder Holly's boyfriend, and run off to Mexico with the loot.
The "music box" is a submachine gun owned by ruthless gangster Larry Shaw (Ronald Foster) in 1920s New York. Larry is working his way up a bootlegging syndicate, but reckons without his decent wife Margaret (Luana Patten), who one day has enough of her husband's activities.
Marty Brill's (Cameron Mitchell) Los Angeles gang plot to assassinate visiting Asian Prime Minister Gourem-Nara (Frank Lackteen). They break into the home of airport flight controller Hal Parker (John Lupton) and hold his family hostage. Brill threatens to kill Parker's wife June (Lyn Thomas), unless he broadcasts a coded message to identify which plane taking off from the airport is the premier's. They then plot to shoot the plane down. Meanwhile, special agents Ben Scanlon (Paul Langton) and Ray Maguire (Logan Field) close in on the gang.
Small time crook Harry (played by Michael Brennan) plans one last job before he retires, but things do not go quite according to plan. Bruce Seton, who played police sleuth Fabian on television, here plays against type as Harry's sidekick 'Nimmo'. The plot is to ambush a truck containing £500,000 of diamonds as it makes its way down Leopard Street; but heavy security means recruiting a larger criminal gang than usual, and inexperienced newcomers threaten to derail Harry's scheme.
A deputy sheriff, Steve Walsh, encounters a trio of young people in Washington between Shelton and Aberdeen in rural Mason County forest and is taken hostage when the girl, Bobbie, produces a gun. Bobbie later tries to seduce Walsh, who is twice her age and resists. Her companion, Roy, tries to push Walsh off a cliff, but plummets to his own death instead.