- "There's a leak... Pissing down on us. Water takes everything apart... down on us. Up from the sewer, that puts us... Water and time could drill a hole in anything."
- ―Dennis, shortly after Waylon drops through the ceiling.
Dennis, referred to as Dissociative Dennis in a document, is a patient at Mount Massive Asylum and a minor antagonist character in Outlast: Whistleblower. He appears only once in the game in a condemned building just above the Vocational Block, where he presumably resides.
After Waylon Park falls through a roof into the Vocational Block's attic, Dennis can be seen through a paneled wall, conversing with his four personalities over varying subjects. As Waylon continues further, he will hear Dennis discussing a plan to use a 'goat' as a sacrifice for Eddie Gluskin, mentioning his hopes to avoid genital mutilation at Gluskin's hands. The "father" hints that they have given numerous men to Gluskin to "cut up" in order to save themselves.
Later, Dennis discovers Waylon and considers him to be a suitable sacrifice, before a resulting chase ensues. Waylon escapes by descending to the lower floor, unaware that Gluskin had taken refuge on the third floor. Once Park descents from the fourth floor, Dennis' personalities individually taunt the man and state that Gluskin's 'bride' approaches, as he raises the attic's staircase.
Dennis does not appear beyond this segment.
Dennis is diagnosed with a mental disorder called Dissociative Identity Disorder (DID), or Multiple Personality Disorder (MPD). He has four expressed identities or personalities: a brother named Timmy, an older brother with a thick speech impediment, their father and their grandfather. All four personalities are active at once and will openly converse with each other, often referring to a life threatening flood. However, whether this flood is a foretelling of a future event or had occurred in the past has had yet to be confirmed. It is suggested that malingering, or a fabrication on reality is the cause for this delusion.
Dennis is a man with brown eyes and no hair, with a pale complexion to boot. The Morphogenic Engine has had very little effect on him, as he lacks any deformities the Engine could have caused, though his face is slightly scarred, possibly due to the electroshock therapy that was conducted on him. His attire includes greyish green patient scrubs and handcuffs around his wrists.
- Despite being a more notable Variant, Dennis has no specially designed or customized character model.
- In the game files, Dennis' name is spelled as "Denis".
- It can be speculated that the stuttering brother's personality is Dennis' original. This is due to the verbal abuse he seems to suffer from the other personalities, to which he seems to willfully ignore. The three alternate personalities also each have a key behavioral trait, a factor that's common in realistic MPD cases.
- It's possible that Dennis was born in the Deep South, as the one constant between his different voices is that they all have a stereotypical "redneck" or "hillbilly" accent and mannerisms, with the grandfather in particular using phrases that could only come out of the darker parts of the Deep South, such as angrily comparing the rest of the family to a bundle of newly whelped possums.