The film kicks off with 15-year-old Rebecca 'Becca' (Olivia DeJonge) as she conducts an interview with her mother, Paula (Kathryn Hahn), for a documentary chronicling her first encounter with her grandparents. During their conversation, Paula reveals that in her teenage years, she fell deeply in love with a substitute teacher, a romance that her parents vehemently opposed. She also alludes to a mysterious incident at the age of 19 that severed ties with her parents for the past 15 years. Paula mentions that her husband found love elsewhere with a woman he met at Starbucks and subsequently moved to Palo Alto. Becca probes deeper about her mother's estrangement from her grandparents, but Paula insists it’s not her place to divulge the past; if her grandparents choose to share that history, that's up to them. Nonetheless, she reassures Becca that despite the years of silence, her grandparents are genuinely kind-hearted and dedicated to volunteering at the local hospital.
Monday Morning
We meet Tyler (Ed Oxenbould), Becca's younger brother, who is 13-years-old and has a knack for rapping. While they travel to Grand Central Station, he laments about his limited cell phone connectivity during their stay with their grandparents. After saying goodbye to their mom, they board a train, where Tyler showcases his freestyling talent, much to Becca's amusement. She reveals to the audience that she agreed to this trip to help their mom bond with a new boyfriend, suggesting that a five-day getaway could rekindle her romantic life.
Upon arriving in Pennsylvania, their grandparents, John "Pop-Pop" (Peter McRobbie) and Doris "Nana" (Deanna Dunagan), welcome them warmly. Tyler’s creativity shines when he freestyles a rap about pineapple upside down cake, while Becca dives into discussions about her documentary ambitions. As they settle into their mother’s old room, the siblings engage in a playful game of rock, paper, scissors to determine sleeping arrangements, with Becca claiming the bed and gifting Tyler a second camera to capture extra footage.
Tyler's curiosity leads him to film Pop-Pop as he mysteriously toils in the shed. Following a brief encounter with Nana while playing hide and seek, the mood turns eerie—Nana, seemingly harmless at first, swiftly becomes a menacing figure, chasing the kids while chanting, "I'm going to get you." They narrowly escape, only for Tyler to later discover a horrifying secret hidden in the shed: a stash of used adult diapers, revealing Pop-Pop's struggle with incontinence. Nana tries to explain, casually emphasizing that they all face such issues to her grandchildren.
One night, amidst a power struggle for control of their lives with their distant grandparents, Becca takes note of Nana's bizarre behaviors, which Pop-Pop attributes to a condition known as "sundowning." As the days unfold, their strange encounters escalate, leading Becca to uncover buried family truths in an increasingly tense atmosphere. She's troubled by the revelation of their grandparents’ deteriorating mental states and the potential threats that loom over them.
Tuesday Morning
At breakfast, Nana unintentionally ruins Becca's computer, adding to the chaos. The kids question Pop-Pop about his wife's well-being, but his attempts to normalize the situation only raise more questions. They play games and make up stories, but things take a dark turn when Becca tries to gain insight into her grandparents' past. Each day's revelations leave them more on edge, as Nana's mental decline becomes more evident, leading to a series of disturbing events, including moments of terrifying confusion and aggression from both grandparents.
As the narrative follows Becca’s quest to understand her family's legacy, bizarre incidents unfold—such as the kids secretly filming strange nighttime occurrences and odd behavior from Nana, revealing an unsettling reality behind their facade.
Friday Morning
Their final day begins with a desperate attempt to maintain distance from their increasingly threatening grandparents. After a frenzied night of terrifying revelations, Becca and Tyler’s survival instincts kick in as they pinpoint the dangers of their grandparents’ true identities. Realizing they must escape before it’s too late, they come face-to-face with monstrous truths, leading to a gripping confrontation where the children fight for their lives, finally unearthing the horrifying secret behind their "grandparents.”
As all chaos unfolds, they manage to contact their mother and reveal their nightmarish experience. Just as they feel trapped in this frightening scenario, the twists and turns of the plot lead to a climactic showdown that will determine their fate.
In a powerful conclusion, the children emerge victorious, but not without emotional scars. The specter of their family's history—filled with past grievances—leaves a mark that they must navigate going forward, ultimately reminding them of the complexity of familial love and the shadows that sometimes loom in family ties. As they fly back to their everyday lives, Becca reflects on the lessons learned, declaring that the past cannot hold them hostage, while Tyler finds comfort in creativity through his humorous rap performances, encapsulating their harrowing journey in a way that's both poignant and meaningful.
