Plot
Dastan, an orphan in the Persian Empire, performs an act of courage in a public market place and is adopted by the king because of it. Fifteen years later, Dastan, his royal-blooded foster brothers, Tus (Richard Coyle) and Garsiv (Toby Kebbell), and his uncle, Nizam (Ben Kingsley) are planning an attack on the sacred city of Alamut, which is believed to be selling weapons to Persia's enemies. Despite his doubts as to whether they should attack a sacred city and his orders to avoid the front-line of the fighting, Dastan leads a surprise attack that succeeds in allowing the Persian army to breach the walls of Alamut. In the confusion, the princess of Alamut, Tamina, instructs one of her guards to take a dagger from a shrine to safety. During the fight, however, Dastan defeats Asoka,Tamina's guard, and steals the dagger. Alamut falls to the Persians and Tamina is captured. In order to pacify the captured city, Tus suggests that he and Tamina marry, which she agrees to only upon seeing that the dagger has fallen into Dastan's possession.
When Sharaman (Ronald Pickup), the king of Persia, arrives at Alamut, he reproaches Tus, his eldest son, for having made the decision to attack the city and although proud of Dastan, chides him for not doing the right thing, as he did before. He suggests that Dastan, rather than Tus, should marry Tamina. Prince Dastan unknowingly presents a poisoned robe, given to him by Tus, to his father, who dies upon donning it. Dastan is blamed for the king's murder and flees Alamut with Princess Tamina. In their first camp, Tamina attempts to kill the prince and recover the dagger, during which Dastan finds out that the dagger can reverse time. During their journey, the duo meet a shady ostrich racing-organizer and tax-averse entrepreneur, Sheik Amar (Alfred Molina), with his knife-throwing African friend Seso (Steve Toussaint). Dastan offers Tamina up as a slave in return for supplies; however, Amar betrays him because he recognizes him as the murderer of the king, for whom there is an "obscene" reward being offered. Dastan and Tamina escape and return to Persia for King Sharaman's funeral; here, Dastan attempts to convince his uncle Nizam that he did not kill his father. Dastan discovers that Tamina has taken the Dagger; however, he then notices Nizam's hands are burned. Garsiv and the city guards appear and attack Dastan and he is forced to escape.
Dastan catches up with Tamina and explains that the villainous brother of the King, Nizam, was behind the murder. Once Tamina finally explains everything about the Dagger, Dastan realizes why Nizam wants the Dagger of Time: to use it with the massive Sandglass to go back in time and undo saving Sharaman from a lion so he could become king. He fabricated the false allegations that Alamut had been dealing weapons to Persia's enemies so that he would have the opportunity to search the city for the Sandglass. However, opening the Sandglass will trigger an apocalyptic sandstorm that would end the world. Meanwhile, Nizam tries to convince Garsiv and Tus that Dastan is trying to overthrow them and should be killed immediately; when this fails, he hires the Hassansins, a group of highly skilled warriors who once served as hired killers for Persian royalty, to slay Dastan.
Dastan and Tamina are again captured by Sheik Amar and Seso, seeking to rebuild his ruined business by turning them in for the enormous bounty. But that night, when everyone is asleep, the Hassansin leader (Gísli Örn Garðarsson) attacks the group by controlling a number of vipers. Many of the group die, but Dastan uses the Dagger and manages to kill all the snakes and saves everyone. The next day, the pair accompanied by Sheik and Seso travel to the secret sanctuary in the mountains near India, where it is possible to seal away the Dagger. However, they run into Garsiv's men. Dastan manages to persuade his brother that he is innocent, only for Garsiv to be fatally wounded by a Hassansin. The Hassansins attack, killing most of the group, while Dastan and Tamina sneak away to the secret place where they can hide the Dagger. Tamina says she is ready to give up her life to protect the Dagger, but Dastan stops her and tells her that he is not ready for her to die. They share a silent and romantic moment, but they are found and attacked and the Hassansin leader manages to snatch the Dagger of Time from Tamina. However, Dastan is saved from the last Hassansin by Garsiv, who then dies of his wounds.
The group returns to Alamut to reveal the truth about Nizam and the Dagger to Tus. They learn that the dagger is being guarded by one of the Hassansins. Seso volunteers for the task of defeating the Hassansin and recovering the dagger. He defeats the Hassansin in a duel but is himself mortally wounded. He manages to fling the dagger down to Dastan before he is taken by the soldiers rushing in at the alarm. Dastan confronts Tus and explains the dagger's mechanics to him and then kills himself; Tus brings Dastan back to life by rewinding time and realizes his brother has been innocent all along. Soon after, however, Nizam arrives and kills Tus, leaving his Hassansin guard to kill Dastan. The Dagger is once again in Nizam's hands, but Dastan manages to defeat the Hassansin with Tamina's help. Nizam goes to the Sandglass caves beneath Alamut, as Dastan and Tamina take a more secret route: an underground tunnel. After a short battle with the Hassansins' leader, fatally wounding him and sending him plummeting to his death in a chasm, Dastan and Tamina kiss for the first time. They then reach Nizam before he can pierce the Sandglass with the Dagger, but he knocks Tamina and Dastan over the edge. Dastan grabs hold of Tamina; knowing he cannot stop Nizam and also save her. Tamina tells Dastan to let her go because it is his destiny to save them, but Dastan refuses to let her go. Tamina professes her love for Dastan, wishing they could have been together, and lets go, plummeting to her death and sacrificing herself to stop Nizam. Heartbroken, Dastan watches her fall. Driven to fight on, Dastan manages to pull himself up. Nizam stabs the Sandglass with the Dagger, but Dastan grabs hold and opens the Dagger, rather than activating it, causing the Sands of Time to flow through freely, rather than destroying the world. Time reverses to when Dastan first obtained the Dagger, now fully aware of all that has occurred.
Dastan stops the siege of Alamut, revealing Nizam's treachery; Nizam attacks Dastan, but is killed by Tus. After apologizing for the ransacking of her city, Tus suggests that perhaps Tamina should become Dastan's wife as a sign of good will. The Prince returns the Dagger of Time to her, which changes Tamina's view of Dastan. Later on, the two take a walk together, and Dastan and Tamina have a small conversation, in which Dastan hints at his knowledge of the Dagger's powers and tells Tamina that he looks forward to a future with her.
