A long time ago, there lived an old couple at the foot of the mountain. The old man was called Ma Liu, and the old woman was called Wu Mei. They had no children, no fields, and no land. They made a living selling tofu every day.

That night, in the dead of night, a whirring sound suddenly came from outside the door. Old Wu Mei woke up and listened carefully, and the sound seemed to come from the mill. She quickly pushed the old man Ma Liu and said, "Old man, listen, there is a noise in the mill!"

Ma Liu didn't believe it: "Don't be suspicious, there are only a few catties of soaked soybeans in the mill, who would steal it? Just sleep in peace!" After saying that, he turned over and snorted to sleep again.

But the problem was that in the second half of the night, the old couple got up and went to the mill to grind beans as usual. When they walked into the mill, they couldn't help but be stunned: the two buckets of beans soaked in water had turned into a jar of soy milk. Who could have done this? The couple were puzzled.

The next night, Ma Liu and Wu Mei were awakened by the whirring sound again. They immediately got up and gently touched the mill. When they took a look, they saw that the mill was turning, but no one could be seen. It was not until the two buckets of beans were ground into soy milk that the mill stopped rotating on its own.

The couple couldn't help but be astonished: what the hell is going on? Could it be that you saw a ghost? On the third day, Ma Liu made a move and plucked the wooden shaft from the stone mill before going to bed. He thought to himself: Without the shaft, I'll see how you grind it! But in the middle of the night, he and Wu Mei went to the mill to see that the stone mill was still turning non-stop, and it didn't take long to grind the beans into milk.

Ma Liu curiously moved the millstone to see that there were a few straws inserted into the hole where the axis was originally installed in the center of the stone millstone, and the couple immediately exclaimed: "Why is there such a strange thing?" They concluded that the grinding was either immortal or a ghost. But they are not related to immortals, and they have no friendship with ghosts. What is going on?

Ma Liu and Wu Mei couldn't guess the reason, but the millstone in the mill kept turning by itself every night. After a few days, Wu Mei said to Ma Liu, "Old man, this grinding is a tiring job. It's not a thing for us to let people do it for nothing, we have to think of something!"

Ma Liu said, "Isn't that so? I think this is the case. In the evening, you can make some white steamed buns and put them in the mill, which can be regarded as our little thought."

In the evening, he and Wu Mei put a large plate of steamed buns into the mill, and when they went to see it at dawn, there was not a single one left. And the beans placed there were not only ground into soy milk, but also made into tofu. Ma Liu only had to pick them up and sell them at the market.

What was even more surprising was that the buyers who ate Ma Liu's tofu all said that it tasted very good. Now Ma Liu and Wu Mei are overjoyed, and the couple put a basket of steamed buns in the mill every night. Ma Liu often quietly went to the door of the mill in the middle of the night to listen to the movement. He really wanted to catch the ghost inside, even if he only caught one, so he could ask what was going on, but he couldn't catch it once.

Later, an old Taoist gave Ma Liu a talisman and said to him, "As long as you use tofu residue to rub a rope that is three feet long, and then use it to put a cover by the door, stick this talisman, and you will be able to catch the ghost."

Ma Liu was eager to see the ghost. After taking the talisman home, he began to make it according to the old Taoist method. After selling tofu, he used tofu residue to rub the rope.

That night, Ma Liu and Wu Mei were rubbing the rope when a little woman suddenly came in and said to the old couple, "Uncle, aunt, don't be busy, you can't rub the rope with tofu residue."

Ma Liu and Wu Mei were stunned.

Wu Mei looked at the little girl and felt that she looked familiar, so she asked her, "You are..."

The little girl said, "Auntie, I'm Wan'er!"

Wu Mei and Ma Liu were taken aback: "Wan'er? You are the Wan'er of the Yan family at the head of the village? Haven't you... already..."

The little girl nodded and said, "Yes, I am the Wan'er of the Yan family at the head of the village.

Ma Liu pointed to the mill and asked Wan'er, "Then... you helped us push the mill together with them?"

"Yes."   Wan'er nodded again and said, "I have received a lot of help from you, and I am here to repay my kindness. I called these little devils here."

Hearing Wan'er say this, Ma Liu and Wu Mei immediately remembered many past events.

Wan'er's parents died when she was young, and she became Yan family's child bride when she was seven years old. But the Yan family did not regard Wan'er as a human at all. They made Wan'er work non-stop all day long, but gave her leftovers and cold rice, wearing rags and clothes, and punching and kicking if she didn't like it. Wan'er suffered for five years, but she couldn't bear it anymore, and escaped from Yan family after being severely beaten. But in the end, because of the long-term abuse, her body was really thin, and Wan'er passed out on the side of the road before running far away. Thanks to Ma Liu's discovery, he quietly carried her home, treated her injuries like a biological daughter, and helped her adjust her body. But who knew Wan'er had just recovered, and one day some news leaked out, and a group of people came to Yan family. He grabbed Wan'er back with his eyebrows and punched Ma Liu. That night, Wan'er threw herself into the river and committed suicide.

At this point, the mystery of the ghost grinding finally came to light, and Ma Liu sighed with emotion: "So ghosts are also so kind!" From then on, he and Wu Mei not only sent more white steamed buns to the mill every night, but also often bought some wine and cooked some vegetables there to reward Wan'er and her little devils.

About half a year later, one night, the mill suddenly regained its previous calm, and the sound of the mill rotating could not be heard. The next morning, Ma Liu and Wu Mei went to the mill to see that none of the white steamed buns had been moved, and the couple couldn't help but tremble in their hearts: Could it be that something had happened to Wan'er?

Three days later, Ma Liu had a dream when he was sleeping at night, dreaming that an old man with a white beard said to him, "Wan'er asked me to tell you that she had been reincarnated. She failed to repay your kindness, so she can only report it later." After saying that, he drifted away. Although the words in the dream cannot be trusted, the couple was relieved to learn that Wan'er had been reincarnated.

Three months later, that day, a dog came to Ma Liu's house. Ma Liu saw that it was so hungry that it was skin and bones, and it was beaten all over the body, so he left it at home for a full meal. However, the dog refused to leave after it was full, so Ma Liu and Wu Mei kept the dog. Soon, the dog gradually grew stronger and changed into shiny fur, and everyone in the neighborhood liked it when they saw it. This dog is also very obedient, not only can he watch the house and protect the yard, but also go hunting in the mountains, and often help Ma Liu and Wu Mei push the mill.

Later, when Ma Liu died, the dog followed Wu Mei to send Ma Liu up the mountain to the ground, lying in front of the grave and crying a lot. After that, he followed Wu Mei closely and never left until one day Wu Mei was lying on the bed and couldn't get up, so the dog stayed in front of Wu Mei's bed. Wu Mei didn't eat or drink, and he didn't eat or drink. Wu Mei died, and he also closed his eyes.

Afterwards, the villagers buried Wu Mei and Ma Liu together, and buried the dog next to their graves. A tablet was specially set up on it, with four big characters written on it: Tomb of the Right Dog.

Unexpectedly, two days later, the words on the tablet became "Wan'er's Tomb".