The play opens with Zhao Jing, a corrupt government official who is in charge of conscripting men into the army. Because he knows that Mulan’s father is an old man with no son, he makes plans to harass the family, expecting a bribe.
Meanwhile, Mulan sits in her home together with her father, mother, and younger sister. Mulan’s father has just received his draft notice and bemoans his fate. His only hope for deliverance would be if Mulan’s cousin, Mushu, volunteered to take his place in battle.
Mushu was orphaned when he was a young boy and has lived together with Mulan’s family ever since he lost his parents. Although he shows great potential, he is lazy, undependable, and is continuously in and out of gangs. When Mulan’s father realizes that his fate rests with Mushu, he is utterly desponded.
Suddenly, Mushu stumbles into the door. Mulan and her father jump to greet Mushu and begin begging him to take Mulan’s father’s place in battle. Before Mushu has a chance to respond, Zhao Jing roars onto the scene. Mulan’s father panics and promises that Mushu will take his place. Zhao Jing stomps off, upset that he did not receive a bribe.
After Zhao Jing has left, Mushu stubbornly refuses to report for duty. Mulan begs her cousin to reconsider, but he is terrified. Mulan begins to belittle Mushu, insisting that she would join the army if only she were a boy. Deeply offended for being called a coward, he challenges Mulan to join the army.
After Mulan accepts the challenge, the two of them agree to exchange places. Mulan dresses as a man and marches off to join the army while Mushu dresses as a woman and tries to learn how to walk daintily.
While Commander-in-Chief Huo Qubing is boasting of his intentions to destroy the Xiongnu, Mulan enters and reports for duty. Huo Qubing takes one look at her delicate features and is about to send her away when Mulan (calling herself Mushu) begins to insist that she is a skilled warrior. Although Huo Qubing is unimpressed, he appoints her vanguard over five hundred men and threatens severe punishment if she does not prove herself to be a successful leader.
Mulan orders her men forward and finds that a battle is already raging between Supreme Commander Wei Qing and the khan of the Xiongnu. In an attempt to better assess the situation, Mulan climbs a mountain and is startled to realize that the Chinese army is suffering a terrible defeat. Just before the supreme commander meets his fate, Mulan leaps down to rescue him. Together, they chase the Xiongnu across an icy sea. While attempting to conceal themselves amongst the icebergs, the entire Xiongnu army drowns. The Chinese army returns to the emperor in triumph.
The supreme commander praises Mulan (referring to her as Mushu) in front of the emperor, declaring that the victory would not have been possible without her. The emperor offers Mulan a prominent position, but she declines. Her only request is that she be allowed to return home.
This anonymously authored play has been translated into English by Shiamin Kwa and Wilt Idema. Their translation appears in their book Mulan: Five Versions of a Classic Chinese Legend (Hackett Publishing Company, 2010).
Kwa and Idema choose to translate the title to this play as Mu Lan Joins the Army in order to distinguish it from Xu Wei's play Mulan Joins the Army. However, because the two plays have identical names in Chinese, I have chosen to give them identical titles in English.