The film tells the story of Princess Taiping who had a dream during the Tang Dynasty. She dreamed that she was riding a snow-white horse with shining silver fur, galloping through a beautiful fairyland-like scene under the bright moonlight.She felt as if she were in a dreamlike world, forgetting the troubles of the world.

The princess was fascinated by this dream and couldn't help but want to know its meaning.So she found a female alchemist named Xuan Ji, hoping that she could interpret her dreams.Xuanji listened quietly to the princess's description, thought for a moment and then said: “This white horse is a Pegasus, symbolizing purity and sanctity.Your dreams are about to come true.”

Princess Taiping was very surprised and excited by Xuan Ji's words. She couldn't wait to ask: "What is my dream?"“

Xuan Ji smiled and replied: Your Highness Princess, your dream is to become a real fairy.You will have immense power and wisdom to change the world.”

After hearing this, Princess Taiping was filled with hope and longing.She began to practice hard, learning fairy arts and horse-control skills, hoping that one day she could realize her dream.

At the same time, Detective Di Renjie of the Tang Dynasty is investigating a mysterious case of massacre.The case involves some prominent families whose members died suddenly and unexplained.Di Renjie discovered a common clue - members of these families are related to a mysterious horse named “Pegasus”.

Di Renjie began to conduct an in-depth investigation into the origin and story behind “Tianma”.He discovers that the horse is a creature from ancient mythology, possessing powerful magic and a curse.It will only choose specific people to tame and serve, and others who come into contact with it will suffer unfortunate fate.

During the investigation, Di Renjie learned that Princess Taiping had been pursuing to become a real fairy and was establishing a relationship with a horse named “Pegasus”.Di Renjie realized that this was a dangerous situation, and he must prevent the princess from contacting “Pegasus” to avoid causing greater disaster.

Di Renjie found Xuan Ji and told her the truth about “Pegasus”.Xuanji expressed her willingness to help Di Renjie prevent the princess's dream from coming true in order to protect her safety.

In the end, Di Renjie and Xuan Ji worked together to successfully prevent Princess Taiping from contacting “Pegasus”.Although the princess lost the chance to become a fairy, she also escaped a life disaster.