15 years after being adopted by King Sharaman (RONALD PICKUP), former orphan Dastan (JAKE GYLLENHAAL) is now one of the royal princes of ancient Persia, alongside Garsiv (TOBY KEBBELL) and Tus (RICHARD COYLE), while their uncle, Nizam (BEN KINGSLEY), serves as the King's most trusted friend and advisor. Although Dastan's blood isn't that of royalty and he's occasionally distracted by rough and tumble activities with his friend Bis (REECE RITCHIE), he's a capable warrior.
To prove that, and when word arrives that the people of Alamut are harboring dangerous weapons, thus necessitating an invasion -- at least in Tus' eyes, Dastan takes the lead and beats his brothers into the kingdom, thus helping ensure their victory over Princess Tamina (GEMMA ARTERTON) and her people.
The victory celebration is short-lived, however, as one of the recovered spoils, a regal robe, ends up killing the King through its poisonous acidity. Since Dastan was the one who delivered it to his adoptive father, everything believes he's the murderer, and thus he and Tamina flee into the desert, a bounty now on their heads.
Needing to clear his name and avenge his father's death, Dastan discovers that a unique dagger possessed by Tamina has amazing powers in that it can stop and reverse time. Realizing it's the reason for the King's murder, Dastan is determined to bring the dagger to Tus, the new king, and explain what's occurred.
But he must not only contend with that story sounding far-fetched, but also Tamina being determined to protect that dagger at all costs. They must also deal with a group of desert people, lead by Sheikh Amar (ALFRED MOLINA) and his knife-proficient lieutenant, Seso (STEVE TOUSSAINT), and a dangerous Hassansin mystic (GÍSLI ÖRN GARÐARSSON) and his band of warriors who all serve as additional obstacles in Dastan's quest.