One year after the previous owners abandoned the house in fear, the Presleys are led to view the property. The estate agent, Barbara Mangold, is keen to highlight that prices have recently plummeted, raising suspicions among the family. At the center of the family dynamics is Frank Presley (Anthony Mackie), who struggles with his relationship with his youngest son Kevin (played by Jahi Winston), an aspiring guitarist.
On the very first night in their new home, Kevin hears strange noises emanating from the attic. Armed only with his mobile phone light, he stumbles upon a ghostly figure. Instead of scaring him, the ghost chuckles, vanishing moments later. Intrigued, Kevin returns to speak with the apparition, whom he names Ernest (David Harbour) after finding his name on an old bowling shirt. Chaos ensues when Kevin's older brother Fulton (Niles Fitch) barges in, bullying Kevin, but Ernest surprisingly intervenes to help. Fulton, eager to show their father, uncovers a video that captures Kevin's initial encounter with Ernest, leading Frank to create a YouTube channel. The footage eventually makes the family internet sensations as they unveil their haunted house to the public.
Eager to assist Ernest in reclaiming his lost memories, Kevin believes the amnesia is linked to past trauma, so he employs various visual stimuli. In school, he meets Joy (Isabella Russo), the neighbor who refers to their house as the "House of Death" due to its forsaken look. As the ghost's presence goes viral, Joy learns that the previous owner, Ernest S. resided there from '65 to '71 but believes there’s an unknown story behind the haunting. When the local cable TV medium, Judy Romano, visits to capture evidence of Ernest, things take a turn for the worse. The crew's startled reactions provoke comedic chaos, leading to Judy’s dramatic exit through a window.
Frustrated by Frank's relentless attempts to monetize the haunting through merchandise and media deals, Kevin decides to take Ernest out with Joy to a bar linked to the ghost's past history. Together, they uncover revealing photographs connecting Ernest to the former owner, leading to increasingly complex revelations about Ernest's tragic life. Unfortunately, one encounter frightens a local child, painting Ernest in a nefarious light, a misconception Frank exploits for profit. Meanwhile, Dr. Leslie Monroe (Tig Notaro), a horror writer with a controversial past involving the CIA’s ghost-capturing project, reaches out to Frank and Melanie, warning them of the potential dangers surrounding Ernest. Ignoring her advice leads to dire consequences as the presence of Ernest on social media escalates.
A twist of fate sends the family on a desperate chase to Oklahoma, where the past unfolds as they seek the truth behind Ernest. Here, a man named Ernest S. (Tom Bower) sheds light on the troubled past of a man named Randy, connected to the very ghost they’ve befriended. As Kevin, Joy, and Ernest delve deeper into the haunting's origins, they uncover dark secrets that draw the attention of authorities and the CIA, culminating in a frantic race across town to evade capture.
As their journey progresses, Kevin grapples with the implications for both him and Ernest. At the climax, poignant flashbacks reveal uncomfortable truths about Ernest’s past. With emotions running high, a confrontation arises, leading to chaos as Frank must confront his role in the spectral unraveling. Just as they think they’ve closed the chapter on Ernest's torment, the future seems uncertain, yet pertinent questions remain about redemption and understanding.
In the aftermath, the Presleys, now wiser, prepare for a new beginning that takes them only a few miles away from their haunted adventures. As Kevin and Joy solidify their bond and prepare for a fresh start, the winding path of memories flickers one last time in the attic, hinting that some stories might never truly end.
