What is the episode in the Water Margin where the dragon hag goes into a black shop and asks for a pig's head?

It's the 21st episode that the evil woman in Water Margin goes into the black shop and asks for a pig's head.

Sun Erniang is an important figure in Water Margin, and is called "Liangshan is the first coquettish". In The Water Margin, he is Zhang Qing's wife, alias Dung Zhuang Xing Muhag. Selling human flesh at Cross Slope and Zhang Qingkai Hotel on Mengzhou Road. Wu Song was sent to Mengzhou to pass through Crossslope, and was killed by Sun Erniang. Wu Song pretended to be drunk and caught Sun Erniang, and Zhang Qing begged for mercy. Wu Song got acquainted with Zhang Qing and Sun Erniang, and Sun Erniang later followed Zhang Qing to Liangshan, presided over the Xishan Hotel in the water margin, ushered in and sent it, and was the 13rd hero of Liangshan. When Song Jiang conquered Fang La, Sun Ernian was killed.

Sun Erniang, a character in the novel Water Margin, is one of the 18 generals in Liangshan. From childhood, I robbed my father, and after getting married, I ran a black shop with my husband Zhang Qing at the cross slope of Mengzhou Road, killing people and selling human flesh steamed bread. When Lu Zhishen and Wu Song passed by their store, they were both killed, but they didn't know each other and became brothers with Zhang Qing. Sun Erniang later went to Liangshan with Zhang Qing, presided over Liangshan Xishan Hotel, and asked for information. After being enlisted, he was killed by Du Wei's flying knife when he attacked Qingxi in the conquest of Fang La. After his death, he sealed the king of Jingde County.

The description of her in the book:

Her eyebrows are fierce and her eyes are fierce.

it's as stupid as a reel, and a wooden stick is like mulberry hands and feet.

thick with a layer of greasy powder to cover up naughty;

if you put it on thick, you will get dizzy rouge, which will directly invade your hair.

The red skirt is beautifully wrapped in belly, and the yellow hair is bright with golden hair.

The arm of the witch in the cage with a bracelet, and the red shirt reflects the hag essence.