Marble Hornets is an alternate reality YouTube web series based on the Slender Man online mythos.

[9] On December 27, 2017, Wagner posted a new photo to his Twitter page, teasing a comic related to Marble Hornets slated for a 2018 release.

[13] Alex abruptly ended the project after only three months of production, left the tapes of raw footage with Jay, cut contact with him, and transferred schools.

Through the footage, he discovers that the filming of Marble Hornets was hampered by the menacing presence of a humanoid figure known as "The Operator".

[13] The Operator appears to have constantly stalked Alex, including while he was on set with his actors, walking his dog to the park, and at his own home.

In response, Jay also sets up constant video surveillance in his home and begins posting the recordings to YouTube alongside the footage from Alex's tapes.

Jay finds Brian's home vacant, in severe disrepair, without functioning lighting, and with a bathroom sink full of dried blood.

Among the tapes, Jay finds footage of himself, Alex, and Tim filming a scene from Marble Hornets, where The Operator is seen watching the men through a window.

Jay visits the park where some filming from Marble Hornets took place, and finds a hidden tape in a red tower there.

Totheark hacks the Marble Hornets channel, and threatens Jay in a video featuring The Masked Man, telling him that this is no longer a game for them, and that they will be coming for him.

Seven months after 'Entry #26' is posted to YouTube, an amnesiac Jay wakes up in a hotel room in an unknown location, with a chest-mounted camera.

Jay uses the combination to unlock the safe in his hotel room, where he finds a large amount of video tapes and a hard drive.

The Masked Man interrupts the reunion, and they wrestle him to the ground and unmask him, discovering he is Tim, one of the core actors in Marble Hornets.

While looking through footage on the hard drive, Jay finds a clip where Alex calls Jessica and tells her he found Amy.

The footage from Alex's body camera shows him bludgeoning a stranger to death with a rock after mistaking them for Jay.

Brian picks up Alex's camera and begins searching for him, but instead he finds Tim laying in a room in a coughing fit.

Jay and Jessica escape and book rooms at a hotel, where they suffer an attack by The Operator and sustain memory loss as a result.

Totheark uploads a video response, entitled 'Reference', which is shot inside of the maintenance tunnel with the audio being distorted clips of Tim yelling at Jay.

The video drives Jay to return to the maintenance tunnel by himself, as he has a hunch that The Hooded Man led him there for a specific purpose.

After being unable to find the shack they had woken up in, they decide to investigate the tunnel from Season 2, where Alex killed a man.

While there, Tim reveals that he was formerly committed to the mental hospital when he was a kid due to hallucinations that he fears were caused by The Operator.

A few days later, Jay and Tim leave to drive to the old filming locations for Marble Hornets to see if they can find any clues left there.

He also finds a tape in Tim's living room, but before he can take it the attic door opens and Alex begins coming down the steps.

Tim is teleported to his house, where he sees Jay's dead body surrounded by papers covered with the operator symbol and text saying "your fault".

A few days later, Tim disposes of his mask and reunites with Jessica, who survived the Operator attack, unbeknownst to Alex.

Wagner and DeLage began working on the webseries after reading about the Slender Man mythos and because both liked the ease of creating a YouTube series.

[33] These funds went towards further projects, including a box set and new supplementary material in the form of scenes from Alex Kralie's Marble Hornets, complete with a trailer for the fake movie.

[34] They also announced that the script would be written by Ian Shorr, that James Moran would direct, and that Doug Jones would be portraying the Operator in the film.

[35][36] In October of the same year, Wagner announced on his blog that the movie had finished filming and it would not be a continuation of the YouTube series but would be set within the same universe.

There are currently 5 issues published including a mini comic about the final fate of Brian Thomas and Alex Kralie.