After the conquest of the Arab caliphate of Bagdad by the unstoppable conqueror Hugalu Khan's devastating Mongol hordes, caliph Hassan is killed when Prince Cassim betrays him, hoping in vain to prevent a bloody revolt, but the legal heir Ali, a minor, escapes and finds the secret of Sesame, the magical desert cave of the forty robbers. When the band finds Ali and sees he has the imperial seal, their headman old Baba virtually adopts the brave boy under the name of Ali Baba; the next ten years they are the only true resistance against the Mongolian oppression. When they tempt to plunder the caravan which brings the tyrannical khan his beautiful bride Amara, daughter of prince Cassim -the present grand vizier-, who as child mixed her blood with Ali's, she -masquerading as her handmaiden- tricks Ali so Mongolian horse guards can capture him; he is delivered for public execution in Bagdad, even after Cassim sees his royal seal, but the other robbers free him and abduct Amara. Her loyal, patriotic servant Jamiel joins Ali and wins his trust for an alliance against the khan, demanding Cassim's life for hers; the princess has Ali's heart and is released on his orders anyway, even before she learns the truth about Ali and reconsiders her betrothal, Ali devises another ploy...