Mary Stauffer [Alyson Hannigan] and her daughter Beth Stauffer [Daphne Hoskins] are abducted at gunpoint outside a salon in 1980 by Ming Sen Shiue [Howie Lai], a former student. A boy named Jason [Harper Postma] witnesses the crime and Ming forces him into the trunk of Mary’s car along with Mary and Beth. Ming kills Jason and then traps Mary and Beth in a closet inside his house, threatening to kill the rest of their family if they try to escape or seek help. He forces Mary to participate in video interviews.
On her birthday, Ming rapes Mary and then records another interview, asking if she’s enjoying her birthday. Mary tells him she cannot enjoy it while she is married. Ming insists he was making love to her, and Mary explains she cannot respond in kind while married. He asks her to make love to him like she does to her husband, calling out his name, and Mary wonders whether he has been listening to her family or even in her house.
Back at Mary's house, Irv Stauffer [Daniel Nemes] discovers a broken basement window, dirty shoe prints, and a small hole in their bedroom floor. He reports this to police Sgt Wyatt Rayburn [Reese Alexander], who suspects someone with electronics knowledge may have been listening in. Investigators suggest examining Mary’s old school yearbooks to identify possible connections.
When Ming leaves the next day, Mary and Beth hear him return and move through the house, pretending to be asleep while music plays from the basement. He introduces his cousin, Brian [Ash Lee], explaining there is an extra layer of padding on the closet floor so Brian cannot hear Mary and Beth.
At day 30, Mary’s voice recalls that hope and her daughter’s love are the things keeping her going, and that she would do anything to keep Beth safe.
Ming arranges a trip to Chicago, renting an RV to take his victims with him. Mary and Beth are bound to a gas line through the floor; if they pull too hard, it could trigger an explosion. Ming has installed listening devices, and he warns that shouting for help will bring harm to others. Mary tries to whisper to some skateboarders outside, but they do not take her seriously.
By day 45, the family is still trapped, with moments of tense calm and peril. On Father’s Day, Beth manages to call Irv and reassures him that she and Mary are safe, though she cannot say when they will come home. Irv asks to speak to the man holding them, but Ming refuses.
One day, Mary decides to act. She pulls the door off its hinges and leads Beth outside, where they move toward the RV and hide behind it as police close in. The authorities arrest Ming at his workplace, and the FBI becomes involved in the case. Mary and Beth are finally reunited with Irv and their son Steven [Miles Phoenix Foley] at the police station.
A postscript reveals that Ming Sen Shiue received a life sentence with parole denied in 2016. Jason’s body was found during the investigation, and Mary and Irv Stauffer remain married, with Elizabeth Stauffer now having children of her own.
