Main plot
In 2024, Madison travels to Gerant Manor after being invited by collector Augustine Lieber (Hannah Morrish). On the way, she meets Linda and Stan (Andrew Krueger), a self-proclaimed businessman. Stan remarks he knows of Linda from Murder Mill, one of her films which is supposedly cursed. Augustine arrives and explains she has invited the group to purchase the reels of Murder Mill that each one of them owns. The group decide to explore the manor after she leaves. They find evidence of high-tech machinery, numerous grim artifacts from history and fiction, and literature related to Frank Stone. They also learn how each of them got their film strips, with Madison inheriting hers from her mother Bonnie (Bermudez) who Linda once knew back in Cedar Hills, and Stan getting his from a "Robbie G." who is now dead. At that moment, a much older Sam Green suddenly appears.
The game shifts to Cedar Hills in 1980, where a young Linda is making Murder Mill with Jaime and Chris. Sam, now the sheriff of Cedar Hills, discovers the group shooting in the now condemned steel mill and orders them to leave. With their camera broken in the confrontation, Linda explains Sam's connection to Frank Stone as well as Frank's kidnappings and murders to Chris, who is not originally from the town. She is inspired and becomes determined to get back in the mill to get shots related to Frank. They head into town to fix the camera, meeting Sam's son Robert (Idris Debrand) who says he can get them back in the mill, and eventually get a replacement from a mysterious shopkeeper of a curiosities store.
The groups sneaks back into the mill to finish the movie, with Jaime's sister Bonnie tagging along. As they explore to get footage, Chris captures strange paranormal energy using the camera. They then discover a room that contains missed evidence of Frank's crimes and even the remains of some of his victims. Robert hurries to fetch Sam while Chris and Jaime wait for him to return. At that moment, the energy surges through the mill and the undead form of Frank Stone manifests before them, unable to be seen visibly without the camera. Chris is suddenly dragged into a portal that opens nearby and disappears while Frank hunts the rest of the crew through the mill, possibly killing Jaime.
Back in 2024, the older Sam accuses Stan of taking his filmstrip from a troubled adult Robert while explaining he is there to stop them from selling the reels to Augustine, though is unable to explain the details of why clearly. Madison and Stan explore further, discovering a gigantic chamber containing a machine called the horologium. Chris suddenly emerges from the device, apparently having travelled through time. Depending on player choices, she can either immediately return to 1980 or remain in 2024. Back with Linda, Sam confuses matters by recalling memories that don't match Linda's and she discovers an archive containing alternate film reels of Murder Mill, along with objects that don't match what she remembers shooting. After Sam finds her again, Linda remarks he should be much older than he actually is and accuses him of not being the Sam Green she knows. After the group reunite in a theatre room, a reel of Murder Mill begins to play which shows the concluding events of 1980.
Frank's spirit pursues the remaining crew of Murder Mill and Bonnie is killed being impaled on a hook. Sam then arrives with Robert after the survivors have fled into the storm drains. Using the camera to ward off Frank, Sam can save Jaime and Chris if they have survived until this point before confronting Frank going after Linda. Otherwise, he and the other survivors can die. In the end, the survivors are able to use the camera to trap Frank's spirit inside the film itself, splitting up the film among themselves to ensure Frank can never return. It becomes clear that the version of Murder Mill the group in 2024 is seeing does not match their own personal histories.
Through collectibles found throughout the game, and from interjections of narration by Augustine herself, it is revealed that Augustine is a member of the Black Vale, a cult dedicated to the worship of the Entity. She manipulated a psychologically vulnerable Frank Stone in the early 1960s to commit his murders in the service of a ritual that would summon the Entity, but Sam's efforts thwarted it. She then began to use the horologium and alternate versions of herself from different timelines to finish the ritual, gifting the camera to the Murder Mill crew under the guise of the shopkeeper. She then began to collect all the potential versions of Murder Mill that held the strong essence of Frank Stone in order to resurrect him. The Sam present in the manor is also from one such alternate timeline, strongly hinted to be the one originally shown in 1963.
With the film now complete, Frank Stone emerges from the projection as an inhuman monster who devours and absorbs either Stan if he has survived up to this point, or one of the remaining group. He then chases them through the manor, potentially resulting in one or all of their deaths in the process. Augustine goes outside to witness the now summoned Entity preparing to devour the world itself. She uses her makeshift trial as an offering for a reward of knowledge, only for Frank to strike her down to let the Entity claim her instead. Any survivors of the manor then find themselves at a strange solitary campfire within the Entity's realm, with those having died replaced by unknown people, while Frank, now dubbed 'The Champion' and one of the Entity's newest killers, awaits the beginning of a new trial.
In an optional pre-credit scene, if Chris chose to stay in 2024, does not have any collectibles, and chooses to walk through the movie screen, she will return to 1980, but in an alternate timeline from before they started their movie, where she stares blankly into her counterpart’s eyes. In a post-credits scene, the horologium inside the manor activates and an alternate Augustine emerges to meet with the older version of herself in a black cloak.
