After Sun Erniang's father died, the couple run an inn at Cross Slope, where they knock out customers with drugged wine, takes their valuables and butchers them to make filling in buns with their flesh.

When Lu Zhishen passes by Cross Slope after leaving the imperial capital Dongjing to escape arrest by Grand Marshal Gao Qiu for thwarting his plan to murder Lin Chong, he eats in Sun Erniang's inn and is knocked out.

Just when Sun is about to butcher the monk, Zhang Qing returns in time and stops her, noticing Lu's unusual appearance.

After reviving Lu and determining his identity, Zhang Qing suggests that he seek refuge with the outlaw band led by Deng Long at Mount Twin Dragons.

Later Wu Song, exiled to Mengzhou for killing his sister-in-law and her adulterer lover Ximen Qing to avenge their murder of his brother, also comes by Cross Slope on his way and eats in Sun Erniang's inn.

Sun suggests that Wu dress himself up with these articles to look like an itinerant priest with his hair let down to cover the tattoo mark an of exile on his face.

Sun Erniang and her husband are put in charge of an inn which acts as a lookout for Liangshan after the 108 Stars of Destiny came together in what is called the Grand Assembly.

The couple participate in campaigns against the Liao invaders and rebel forces in Song territory following amnesty from Emperor Huizong for Liangshan.