I suppose it's possible that this would have had more impact in its intended format, in which the entries were released at short clips, one at a time on Youtube, as part of an an 'alternate reality game'. However, watched all together, though the results are close to feature length, the overall effect is as an amateurish stab at pseudo-reality, with camerawork that makes The Blair Witch Project look like Lawrence of Arabia. It centres on Jay (Wagner), who gets a load of tapes from a college friend, Alex (DeLage); the tapes include footage from Alex's student film, Marble Hornets, during the course of which Alex grew increasingly volatile, before abandoning the project and, eventually, leaving the area. As Jay watches the tapes, he tries to piece together what happened to Alex. It seems he found himself being stalked by a mysterious entity, known in Internet lore as 'The Slender Man'. As the encounters became more invasive, Alex's defenses became more extreme. And now, it seems that Jay's investigation has brought him to the Slender Man's attention, and he is suffering from blackouts, where he doesn't recall anything.
There's a decent idea in here, but the execution is poor, unfocused, and apparently unaware of every horror cliché the genre possesses. For instance, Jay's decision to go investigate a house he feels might be significant - which, of course, he visits in the middle of the night, with a torch. Matters are not helped by the truly dreadful hand-held photography. While it's nice that epileptics don't let their illness stop them, I think they should probably stop filming during a Grand Mal seizure. The occasional intriguing moment, with the Slender Man's admittedly creepy appearance, are far from enough to overcome the film's obvious shortcomings, and instead provide compelling evidence that the 'faux documentary' approach is sometimes just a crutch, used by those too lazy to bother writing a proper script.