Antonio is the humble servant of a rich family, governed by the Marquis Gastone. He is a young man madly in love with Lulu, but she betrays him, and he desperately enlist in the foreign legion. The old Marchesa, his mother, persuades Antonio to enlist to watch over Gastone, and so he arrives in Arabia. There Antonio is led with barrel (because enlistment is secret), and is exchanged by Muslims for their sheikh, who came to lead the revolt against the western invaders. The vicissitudes follow one another, especially when the rebels discover that Antonio is not the Sheikh, and so, having also escaped a death sentence, Antonio ends up in a secret passage, in the lost city of Atlantis, where he meets the beautiful Queen Antinea.