During the Qin dynasty, the general Meng Yi is tasked with escorting Ok-Soo, a Korean princess, back to China to marry the Qin emperor. Along the journey, a Korean warrior attempts to seize her back but Meng Yi saves her. Ok-soo falls in love with Meng Yi and displays her affections for him openly, but Meng honourably rejects her and successfully completes his mission. The Qin emperor becomes critically ill later and he sends Meng Yi to find the elixir of immortality, the only thing that can save his life. The guards escorting the elixir are ambushed by rebels on the orders of the treacherous prince and chancellor. Meng Yi hands over the elixir to his deputy, Nangong Yan, before dying in the ensuing battle. Although Nangong Yan manages to bring the elixir to the emperor, the prince and chancellor wanted Nangong Yan and Ok-soo to test the validity of the elixir and force them to consume the elixir, condemning them to imprisonment in the Qin emperor’s mausoleum for eternity.
In the present-day, Jack, an archaeologist, is Meng Yi’s reincarnation, and he often dreams about his past life. One day, his friend William invites him on a quest to find a rare material that can create a field of zero gravity. They travel to a floating tomb of a Dasar prince in India, where Jack discovers a painting of the princess he has been seeing in his dreams. Jack also learns that during a mission to the Qin Empire, the Dasar prince brought treasures and women as gifts. In return, the Qin emperor offered him one of his concubines and asked him to choose, but refused when the prince chose his favourite, Ok-soo. Instead, the Qin emperor gave him a painting of Ok-soo and the Qin Star Gem. William removes a strange black rock from a feline statue, and accidentally collapses the zero gravity field holding up the tomb, resulting in its destruction. William manages to escape but Jack leaps off a cliff and falls into a river. He loses consciousness and drifts along with the current until he is saved by Samantha, an Indian peasant girl. Samantha brings Jack to see her uncle, a Kalaripayattu guru, who tells Jack to take the sword he found and fight with one of his students. During the fight, Jack has a recollection of a duel he had with the Dasar prince in his past life, and briefly recovers his fighting skills from his life as Meng Yi. Samantha’s uncle enlightens Jack about his past and future, and Jack succeeds in returning home safely and he delivers the sword to the National Museum of China as a national treasure. His action angered Professor Koo, the leader of the syndicate that has been funding Jack and William’s treasure hunt.
After extensive research, Jack and William conclude that the anti-gravity material is actually a fragment of a meteorite that fell to Earth during the Qin dynasty. They find the exact location of the Qin emperor’s mausoleum, concealed behind a waterfall. The massive tomb contains the strongest fragment of the meteorite, which is powerful enough to make the tomb become a floating palace. Jack meets Ok-soo and Nangong Yan still alive inside the tomb and they mistake him for Meng Yi. Just then, Professor Koo and his men enter the tomb and attempt to seize the immortality elixir, leading to an aerial fight between both parties. William accidentally breaks the balance of the field after removing a piece of the meteorite and causes the tomb to collapse on itself, and dies from drowning in mercury. While Jack is escaping from the collapsing tomb, he asks Ok-soo to come with him, but she refuses after realising he is not Meng Yi and says she will wait for the real Meng Yi forever because she believes he still lives.
Before the film ends, Jack is seen at home with a published copy of The Myth, a book written by him about his adventure and his experiences which he dedicates to William.