The black antidote

Two hundred years ago, there was a witch in the area who was known for making potions. Her only daughter was unable to have children, so she asked her to make a potion for her so that she could have children, but the potion that this old woman made changed the fate of this family. Her daughter spared two twin girls, and then the old woman died and found... Her daughter was wearing a necklace that the old woman wore under her clothes. It was a black rope tied to a bottle of black antidote. So the girl kept that necklace and after that she had a vision that her mother told her to keep that necklace and give it to her wisest daughter and pass it down through the generations.
Two hundred years have passed and every girl in this family gets married and gives birth to twins. She chooses the wisest one and gives her the necklace at the age of 18.
The two heroines of the story are twins who work to rid the world of evil through murder and fall in love with a detective.