A teen girl named Marie, who is having breathing difficulties is being cuddled by a woman in the back seat of a car and being rushed to a hospital by a male driver. After getting down at the hospital and while carrying the girl inside, the man warns the woman saying "Not a word".Next, we see a family eating at a table. Don and his wife Renee are raising two daughters Amy and Sara. Sara is rebellious and sneaks out to dance at a bonfire with her motorcycle-riding boyfriend. His name is Chris, and he also plays the guitar. He sings Sara a song and tells her that he loves her.When Sara comes home the next morning, Don is pissed and screams at his daughter. He says as long as she lives in his house, she will follow his rules. Sara makes plans with Amy and Renee to move out on her own when she becomes 18. Don overhears the conversation and preps his bomb shelter in the basement. He plans to lock his daughter inside so she can't leave him.While Renee is out shopping, Don asks Sara to help him move stuff in the basement. Then he locks her in and soundproofs the room. She is literally trapped in a bomb shelter and has no way out. The bin is full of clothing. We get a day counter. This is Day 1 of many, many, more to come.Sara is living like a caged animal. The keypad has three tries before shutting down the air circulation. Sara uses pots to piss in and takes every opportunity to scream for help and fight to be freed. Don tells her that she will earn her privileges and is being punished for her behavior. Then he rapes his own daughter.Renee thinks her daughter has run away and calls the police. Don and Renee talk with the police, who think Sara is a runaway, and there isn't much they can do because she is eighteen.Day 7- Sara is bruised and battered. She thinks of Chris to get herself through the trauma she is experiencing. Ironically, Chris shows up to question Don about where Sara is. Don lies and says she ran off with another man named Stevie.Day 21 - Don goes downstairs, forces Sara to put on a red dress, gives her a birthday cake, and asks her what she wants. She says she want to be released, to which he says that it is too early. Then she asks for a TV, to which he says she has to earn it. Then she asks for a clock. He agrees and ask her to come closer. (Probably she gets raped again)Day 38 - The next time he comes down, she is ready and attacks him with a makeshift weapon. (A corned beef can lid attached to some wood.) But he easily avoids the attack and beats her and probably rapes her again.Fast Forward from Day 39 to Day 354- Sara is pregnant with her father's child/her sister. She delivers her baby with no medical assistance or proper medical hygiene. She is using a nursing book to prepare for the baby. She names the baby Marie.Four years later, Sara is raising her daughter and she is also pregnant again. They are all locked in the basement together and only have one another. Sara seems calmed down and talks with Don, even offering him tea once he visits. Don has got a promotion and tells that he is going to have a new office. He also has provided her with some basic necessities, such as a table, cupboards, a mattress etc. Sara asks him whether he could release them to which he responds angrily. But he later provides them with a TV as a Christmas present.Year 7 - Sara has given birth to a son (named Michael) and all are living in the basement. The daughter Marie seems to be sick and Don provide some pills, but Sara says they are not for kids and does not know what the dosage would be. She demands Marie needs a doctor, but Don just leaves.Chris still is looking for Sara and shares with Amy the lies he heard from Don about Sara eloping with Stevie. Amy admits that her father has been abusive with her mother and thinks that Don did something to her sister. Then she confronts Don and accuses him of doing something. Renee wants to go to a private investigator, which sets Don off. They argue, and Don drops his basement keys. Amy picks them up and snoops around the basement, only to be caught by an aggressive Don.Sara has her third baby (a boy named Thomas) and convinces Don to leave the baby on the doorstep with a note from her asking to take care of her newborn baby. Don leaves the baby for Renee to find. He finds a smaller note Sara left asking her mom to call the police because she is trapped in the basement.14 years. The children, Marie and Michael, are growing up. They have social anxiety from being locked in a basement bunker their whole lives. They do not understand how horrible the situation they are in really is.17 Years. In the basement lock up they notice a leak in the ceiling and start digging their way out with a spoon. Meanwhile Renee has some bonding time with grandson Thomas. Sara spends all night digging; she is also pregnant again. The hole leads to the front yard, and she flashes a light signaling a neighbor for help. When the neighbor goes to the front door and tells Don, he goes downstairs and beats his pregnant daughter, causing her to miscarry.18 Years in captivity, Don fills Sara in about her other son living just above them named Thomas. He uses Thomas to turn Marie and Michael against their mother. They demand to be let out, and Sara can't take it. She freaks out and collapses on the floor, crying. She thinks of her boyfriend Christopher and the love he showed her. Sara tells her children the truth about Don. The kids understandably are overwhelmed. Marie is asthmatic and has trouble breathing due to limited air supply in the basement.19 Years - Don comes down to the basement and has an argument with Sara about rationing food. Michael gets angry and tries to beat up Don. That only makes him angrier.Above ground, Don isn't doing so great either. He constantly fights with his wife, is fired from his job, and his house is in foreclosure. He is tired of taking care of Sarah and the kids and funnels carbon monoxide into the basement (by keeping the car started) air vents with a hose while they sleep. Thomas catches Don in the garage and wonders what his grandfather is doing. Don has a change of heart and doesn't kill them. He goes to the basement to check on them and we see that they are okay and still sleeping.20 Years - Marie has breathing problems and has an asthma attack so bad that she needs medical attention. Sara begs Don to take them to the hospital, and she even calls him "Dad." He rushes them to the ER. It is the same scene we saw at the start of the film. Doctors fight to save Marie. Elisabeth Röhm plays a concerned doctor and asks about Marie's medical history. Sara asks to go to the bathroom, and Don refuses to let her go. She spills water on Don's paperwork and makes her way to get help while he gets a new form. Sara tells the doctor everything. Don is arrested and put away for life.Renee is horrified to learn the truth about what happened to her daughter at her husband's hand in her own house. The family all move in together. Motorcycle Chris shows up and takes Sara out for a picnic. They talk about their teenage plans for the future, and Chris apologizes for not trying harder to find Sara. Then they go for a ride together. (thanks to lifetimeuncorked)