Journalist and man-about-town Marcello struggles to find his place in the world, torn between the allure of Rome's elite social scene and the stifling domesticity offered by his girlfriend, all the while searching for a way to become a serious writer.

Kerwin Matthews, playing a dissolute drifter down on his luck, is stranded in a cheap bar in France where he falls for Annette, the pretty daughter of the proprietor, played by Nadia Gray. Nadia Gray gradually shifts the young man's attentions to herself, rather than her daughter, and together Matthews and Gray concoct a plot to help Gray's estranged husband, now a homicidal maniac confined in an institution after a grisly series of killings dubbed "The Acetylene Murders" by the press, out of the mental institution so he can escape from the country.