My thriller Idea : "Cult"

My horror/thriller idea:

"Cult"

A young successful couple go to visit girls hometown to search for her parents and relatives, because her mother was sent away to live in a big city when she was very little and told her daughter to find out about her origins, it was her death wish. After visiting the town hall to search for some records, they find an address of the house where she was born. We can see somebody following and spying on them with evil eyes. Strange things happen, an old woman recognizes a scar on her face and runs away. They find out that the house is just outside the town. When they stop on a gas station, they have a chat with a policeman, and tell him where they are going. He tells them that the place is believed to be cursed. The couple dont trust the policeman and continue to drive to the house. After looking around the house and not finding anything interesting they decide to leave. However, some evil creature/person captures the pregnant girl and kills the guy. Police doesnt find anything on the crime scene and decide to close the case. However couple of months later a baby girl is found in the forest by some campers.
DNA tests show that she is a daughter of that missing girl. She grows up with his aunt and uncle. Eighteen years later she wants to find out about his parents death and goes to the same place with her friends. Her friends get killed one by one and then she and her boyfriend get dragged into the forest. They come to senses and see a lot of caveman-looking evil maniacs in the middle of a ritual, in the end of which the teenagers die. She finds out that his mother and father were killed this way as well. The girl's boyfriend dies and she manages to run away. She is chased by the maniacs in the forest and in the end escapes. She finds a policeman in the town nearby and tells him to go and arrest the maniacs. However in the end we can see that police couldnt find any evidense of cult existance, and the girl ends up in an asylum. When she enters the mental clinic, we can see that one of the maniacs is watching her from the forest.