Pinmook's mother was a maid for her father, So one day her father got her mother pregnant, and the grandmother wasn't happy. Her grandmother then make Pinmook's father marry 3 wives to get rid of Pinmook's mom but never succeeded.
One day Pinmook's dad went on a bussiness trip, so the grandma and the 2nd wife assaulted Pinmook's mom and lock her up because she was pregnant with Pinmook and she wouldn't leave Pinmook's dad. Later on, Pinmook's mom left and then her dad came home and they lied to her dad that she had another men and no one had seen her since. 20 years had passed and Pinmook later found out about her family background. She then go back to the house as a servant by the name of "Pin" to reclaim her will. When she got there she found out about her father's death.
The 1st wife is now the head of the house and she had adopted Atiya, and wanted to Atiya to steal the assets of the family.
(Source: AsianFuse Wiki)