Alex is approached by his friend, Chris, who believes that his home may be haunted. After witnessing several strange occurrences at Chris's house, which suggest the involvement of an intruder rather than a ghost, Alex invites Chris to stay at his house. The two hear a strange noise and discover Chris's attic to be open, with newspapers detailing the disappearance of Marc McComber - who once lived in Chris's house. It is later discovered that the intruder is a masked man known as KindVonDerRitter. After the strange occurrences continue, Alex helps Chris move back into his house, where he discovers and chases off a masked man in a suit.
While visiting their friend, Greg, Alex and Chris discover Kind von der Ritter wielding a knife and escape into Greg's house, where they remain until the man eventually leaves. Soon after, the two attend a party at Greg's house, although discover that the host is nowhere to be found. With the help of Jesse, another friend, Chris breaks into Greg's house where he finds Greg dead. Alex and Jesse followed Chris in. They find Greg dead and Chris unconscious, having encountered the Slender Man. Detective Amsel later blames Greg's murder on a supposed serial killer known as "the Tall Man".
Looking for answers, the three friends search the abandoned day camp across the street from Greg's house, where they discover a black book, which was seemingly written by a cult. Following a lead found within the book, they then visit the Atlantic Test Site, where they once again encounter Kind von der Ritter. When Alex and Chris later stay over at Jesse's house, believing that he may also be in danger, KindVonDerRitter enters during the night and leaves behind his knife, seemingly as an offering of peace. The three later revisit the day camp, entering the basement of one of the buildings, where they discovered the meeting room of The Order.
Not long after, KindVonDerRitter emails a video to Alex, which seemingly depicts a sacrificial ritual being performed by the Order. One night, three cultists appear outside of Alex's house, prompting him to chase them into the nearby forest. Alex calls Chris over and two enter the woods, discovering three garbage bags, likely containing the cultists' remains. The next day, they locate the 'cultists' masks in a nearby part of the forest before being chased by the masked man in the suit, until he is tackled to the ground by Kind von der Ritter, allowing them to escape. Upon exiting the woods, the two encounter the Slender Man and retreat into Alex's house to escape. They later decide that filming is proving unhelpful and agree to stop.
Alex later helps Chris interview Heather McComber, the owner of a chest, which once belonged to her grandfather, Marc McComber. Alongside Jesse, Alex helps Chris steal the contents of the chest: classified military documents pertaining to the Princeton Experiment. Soon after, Alex and Chris visit the Rainwood Memorial Elementary School to speak with a representative who Daniel Shipman, an accomplice of theirs, had set up a meeting with. Upon entering the school, the two discover the representative to be their friend, Matt.