The Xie brothers (Xie Zhen and Xie Bao) are arrested in Dengzhou (登州; in present-day eastern Shandong) for smashing up the house of one Squire Mao who has pocketed the tiger they shot to claim reward at the prefectural office. Yue He, a jailer in the prison and a distant relative of the Xies, takes the news to their cousin Gu Dasao, warning that the brothers could be murdered in prison. Gu's husband Sun Xin enlists the Zous to help in the rescue. Sun Xin also compels his brother Sun Li, the garrison commandant of Dengzhou, to join the plan. After they extricated the Xies from prison, the group flee to join the Liangshan Marsh.