In ancient Baghdad, the poet Omar Khayyám, Vincent Price searches for his friend Sinbad, the son of the legendary sailor, and finds him outside the palace of the Khalif. Although a reward is offered for Sinbad’s capture, he slips into the palace undeterred and uses Omar’s poetry to charm Nerissa, Lili St. Cyr the enigmatic harem girl who draws the eye of those who wander the court. When a slave exposes him, both Sinbad and Omar are seized and brought before the Khalif, setting off a chain of trials that threatens to unravel everyone’s fate.
Also on trial are Greek scholar Simon Aristides and his daughter Kristina, Mari Blanchard a childhood friend of Sinbad, who have been falsely accused of theft. The Khalif, furious at the audacity of these alleged offenses, orders the execution of all four, but his adviser Jiddah counsels restraint and urges him to meet Murad, an ambassador of the menacing force led by Tamerlane, whose invading armies loom over the city. Murad, hungry for hospitality and leverage, presses for time as his troops prepare for an assault that could topple Baghdad.
To save Kristina, Sinbad reveals that Simon possesses the secret of Greek fire, an explosive formula that could turn the tide of any siege. Simon agrees to demonstrate the weapon in exchange for freedom for himself, Kristina, Sinbad, and Omar. The Khalif consents—though Sinbad and Omar remain imprisoned. During the demonstration, Simon hypnotizes Kristina to recite the formula. Unbeknownst to them, Jiddah and Murad watch intently from a distance, unable to discern the exact chemicals being used, even as the display suggests a power that could rewrite their destinies.
Impressed by the demonstration, the Khalif promises to release Sinbad and Omar the next morning. Kristina confides in Ameer, Sally Forrest who is in love with Sinbad, asking her to relay the news of his imminent freedom. Despite her jealousy, Ameer delivers the message, but soon discovers that Kristina has vanished and Simon has been murdered. Murad has abducted Kristina and siphoned off the precious chemical bottles. Before Ameer is captured by Jiddah, she manages to send a warning via carrier pigeon.
While torturing Ameer for information, Jiddah discovers a tattoo linking her to the Forty Thieves—a legendary group once led by Sinbad’s father. Ameer confirms that their descendants remain active, leading Jiddah to suspect that the warning reached the right hands. Meanwhile, Sinbad and Omar escape their cell and confront the Khalif, who is blindsided by the turn of events. Sinbad offers to rescue Kristina in exchange for gold, a formal pardon, and the promise of becoming second in command. The Khalif agrees, though he remains unaware of Jiddah’s treachery toward him.
In the desert, Ameer finds Sinbad and Omar and reveals that Murad is traveling with disguised Tartars posing as merchants. The Forty Thieves plan an ambush at the caravan’s first camp, and Sinbad hides underground near Kristina’s tent to slip in covertly. When Murad unknowingly removes Sinbad’s breathing reed, the pirate duo are forced into the open, and Sinbad manages to rescue Kristina from danger.
The Forty Thieves—revealed to be all women—launch a surprise assault and reclaim Simon’s chemical bottles. Inside their hidden lair, Sinbad uses the ancient command open sesame to gain entry with Kristina and Omar. The thieves’ leader, Ghenia, grants refuge, as Kristina confesses her love for Omar, while Ameer rebuffs Sinbad’s wandering affections, choosing loyalty over desire.
Murad’s forces soon close in on the thieves’ cave. Sinbad hypnotizes Kristina again to recall the Greek fire formula, and with the Thieves’ help he harnesses the explosive power to blunt Murad’s army and turn the tide of the conflict. In a final duel, Sinbad slays Murad, restoring a fragile peace to the region. He persuades the Forty Thieves to accompany him back to Baghdad, where they will be pardoned and welcomed as allies rather than rebels.
Back at the palace, the Khalif contemplates punishment for Sinbad, unaware that Jiddah’s betrayal has been laid bare. When Sinbad arrives with Kristina and the victorious raiders, the Khalif embraces him, orders Jiddah’s punishment, and rewards those who stood by him. Omar is appointed royal poet, the Forty Thieves are granted clemency, and Sinbad is named second in command. In a final, hopeful moment, Sinbad turns to Ameer and asks for her hand in marriage, offering a life where duty and affection can coexist—even as the city faces the shadows of a troubled past and a treacherous present.
