Jay (or J, has his name is initially given) is the de facto protagonist of Marble Hornets. In 2006, his college buddy Alex Kralie was filming a student project known as Marble Hornets, and suddenly ceased the project due to many factors. Jay, curious to the reason, and to keep Alex from burning the tapes as he has planned, convinced him to hand them over. Jay was so rattled by Alex's attitude that he forgot about the tapes for three years, until he found them in the back of his closet. He then began searching through them to uncover the truth of the fate of the student film project, and began uploading anything of interest to YouTube.
Jay's status as a reliable narrator is often called into question after some of his actions, and at times, he also seems to be overly clueless and naïve, pointing out the obvious and doing the precise opposite of what would be logical in a given situation. However, he has shown some moments of cunning, especially in later entries, and may be finally catching on.
Following his rediscovering of the tapes, Jay began to notice something strange occurring in a few scenes. In a clip that would become Entry #1, Jay witnessed a tall, faceless man in a business suit standing outside what appeared to be Alex's House. As time went on, this man began to reappear in Alex's life; Jay also began to notice audio-visual distortion in some of the Marble Hornets footage, as well as some inconsistencies with his own memory. Jay, for example, did not recall being part of the Marble Hornets crew despite appearing clearly on-camera during production.
Eventually, Jay decides to some sleuthing to determine what is going on. He sets up an interview with former Marble Hornets actor Tim in Entry #15 and starts making trips to The House in Entry #16. All the while, he begins exhibiting symptoms of The Sickness and losing gaps in his memory - he had no recollection of what happened after being assaulted by the Masked Man in Entry #18 or the three-hour gap of his disappearance following The Masked Man's infiltration of his bedroom in Entry #19.
Entry #23 and Entry #24 deal with Jay seemingly being teleported around first The House and then his own home; when in The House, doors that should logically lead to complete other areas serve to only send him around in circles, and at his own place, he opens the door out of his bedroom and never appears out the other side, re-entering his room two hours later, with no recollection of where he was.
Jay, feeling unsafe due to the events of Entry 24 and Entry ######, relocates to a hotel. Entry #25 shows a news report that his apartment had been burned down. Jay announces his retirement from investigation due to the stress, but recants when he receives a tape from Alex showing The Operator appearing before himself and his girlfriend, Amy. Jay vows to find out what happened to Alex.
Seven months later, Jay wakes up in a strange hotel room in an unfamiliar area, with no memory of the duration between Entries. He sets out to find out where he is and how he got there, and meets his neighbor, Jessica, who is acting a bit peculiar. It also becomes apparent to Jay that he and Jessica are the only patrons of the hotel and that the staff are the only people other than the two of them there.
Jessica eventually comes clean and confesses that she, too, is missing a large chunk of her memory and has no idea why she's in the hotel. Jay tells her to pack up her stuff and get ready to leave with him. After Jay packs, however, he finds her room empty except for a scrap of paper with "11Ⓧ2" written on it. He tries this combination on the safe in Jessica's room, but it is unsuccessful; he next is able to open his own safe with it. While digging out the contents, he is assaulted by The Masked Man, who is noticeably hobbling. Jay managed to escape the hotel with the safe's contents, but Jessica is nowhere to be seen.
Jay discovers that within the safe were tapes and a hard drive containing footage from the seven month gap. The the first video shows him driving to the return address on the tape he got from Alex back in Entry #26, which turns out to be an abandoned building. He returns to this building in Entry #35, encountering Alex, and then The Masked Man. The Masked Man attempts to stab Alex with the knife Jay lost in his initial scuffle with him, but he is subdued by Alex. Alex pulls off the mask to reveal that it is Tim. Alex attempts to smash Tim's head in with a rock, but only succeeds in bashing his leg.
Later, Jay follows Alex through the woods, and Alex tells him the history of the area, which seems to hold some clues as to the origin of The Operator. Jay does not seem to grasp the significance of the story.
In another instance, after agreeing to meet Alex at Rosswood Park, Jay gets bored and ventures into the woods himself, in which he encounters The Operator. He runs and drops his camera, but finds it inside his car when he and Alex get back to the parking lot.
However, in entry 80 Jay was shot (and presumably) dead, Alex being the gunman.