The Infinitum Research Intercept Squad, also known as IRIS, is a well-trained, fully armed, and coordinated unit specifically designed to capture or kill escaped experiments.

Their current mission is to hunt and kill Subject 617, a genetically modified individual who has been given SuperStrength, SuperSpeed, and the ability (and need) to feed off human corpses to heal.

Oh. And he's [[VisibleInvisibility invisible]]. They call him "The Hidden" nowadays.

''The Hidden: Source'' is a horror-themed multiplayer FirstPersonShooter based on the [[VideoGame/{{Half-Life 2}} Source]] engine. Everyone plays on one team (IRIS), but every round, one player is chosen at random to be the Hidden. The Hidden runs faster and jumps higher than any of the IRIS players, he can grab onto walls, he can see enemies ''through'' walls, and - this is important - he's ''invisible''. On the downside (for him), there's only one of him, and a whole lot of IRIS members; also, he only gets a knife, while IRIS is armed with guns. The Hidden wins by killing all of IRIS before time runs out. IRIS wins by killing the Hidden. Of course, points don't really matter because the teams are pretty much random, so the goal is really just to [[ParanoiaFuel piss yourself in fear]].

The game began life as a ''VideoGame/{{Half-Life|1}}'' modification, but this version was never publicly released and was only played by the author's friends at university. It was remade for the Source engine by those same friends. The game was also a finalist for "Best Mod - Half-Life 2" at the 2006 Independent Games Festival (see [[ here]]).

Free to download and highly recommended... though not for the faint of heart. If you've got ''VideoGame/{{Half-Life 2}}'', ''VideoGame/TeamFortress2'' or about any Creator/{{Valve|Software}} game and {{Steam}}, [[ check it out!]]

Not to be confused with the BMovie where Claudia Christian [[BestKnownForTheFanservice played a stripper (and some other stuff involving aliens or something).]]
This game provides examples of:

* AbsurdlySpaciousSewer: Partly. The Sewers map is big enough for humans to walk around in, but the confined tunnels (not to mention the water) are particularly challenging to the Hidden.
* AirVentPassageway: Certain maps have airducts and whatnot in the ceiling that the Hidden can use to sneak around. Other maps have similar ducts in the wall that particularly cowardly I.R.I.S. players try to barricade themselves into.
* AuraVision: Used by the Hidden and drains your SprintMeter when used.
* AxCrazy: The Hidden aka The Stalker (depending on the version you're playing). Very much so.
* BackStab: The pig stick technically doesn't require you to stand behind your target, but it's a lot easier that way.
* BeethovenWasAnAlienSpy: A more recent one: stem cell research is a cover for the genetic research that produced the Hidden, which has been going on since the 1950s.
* CatScare: Despite the lack of cats, the Hidden's ability to toss crates and other objects allows him to distract players in a similar manner, usually just before pouncing.
** In several maps, there are also several vents that have the same hissing and visual effect of the Hidden.
* ColbertBump: As of September, 2012, the game has recieved a massive surge in popularity from being featured in a popular [[ video]] from the [[LetsPlay let's player]] SeaNanners.
* DamnYouMuscleMemory: Pro Hunters in ''VideoGame/Left4Dead'' may have a hard time adapting to the Hidden's pouncing controls, especially the wallgrab.
* EasterEgg: There's an [=XBox=] hidden (or not hidden) in every level...and with VideoGame/{{Half-Life 2}}'s [[WreakingHavok physics engine]], it's possible to be killed by it.
** There's also a teddy bear in every level.
* EnemyChatter: Both sides have a selection of quotes their characters will say in-game. The I.R.I.S. team's are mostly standard tactical quotes ("Enemy spotted," "Man down") as well as challenges to the Hidden ("Bring it!") The Hidden's hissing whispers, on the other hand, are purely intended to terrify the other players - "I ''seeeee'' you..." "Mmmm, fresh meat." "Look up..."
* ExactlyWhatItSaysOnTheTin: He's ''hidden'', see.
* FragileSpeedster: Arguably the Hidden. He is rather fast, but he has equal health to the soldiers he fights. The soldiers, however, have guns...
** GlassCannon: The Hidden's Pigsticker attack can OneHitKill an IRIS soldier if it connects.
* GatelessGhetto: The urban maps.
* HealThyself: The Hidden can eat corpses to do this.
* HiddenInPlainSight: In the right circumstances, an unmoving Hidden player is effectively invisible.
** He is invisible. Just more invisible in the right circumstances.
* HuntingTheMostDangerousGame: I.R.I.S. is hunting the Hidden, while the Hidden is in turn stalking them.
** In gameplay mechanics, generally the Hidden needs to wipe out IRIS to win, however.
* InfraredXrayCamera: The Hidden has a special "aura vision" mode he can activate, which allows him to see player's glowing outlines, even through solid objects. The distance at which a player's aura is visible is based on their remaining health; the closer to dead you are, the more clarity the Hidden has when hunting you...
* {{Invisibility}}: Clearly.
* KnifeNut: The Hidden is able to take down the equivalent of an entire SWAT team with a single knife.
* LaserHallway: The Sonic Alarm. Enough players use them, you can lock down an entire section of the level! Or lull yourself into a false sense of security...
* LaserSight: The I.R.I.S. team can put these on their guns to help locate the Hidden.
* LegoGenetics: To be fair, the backstory does say it took nearly fifty years of research to figure out how to make him invisible.
* LeParkour: Pouncing and wallgrabbing for the Hidden.
* LudicrousGibs: Instead of making a standard knife slash, the Hidden can deliver a powerful Pigsticker strike that kills in one hit, but leaves little for him to recover health off of afterwards.
* MadBomber: The Hidden gets three bombs that can be used to great effect in the right circumstances. His insanity is indubitably a given.
* OneBulletClips: Averted. Many a player has reloaded with half a clip or magazine remaining and run out of ammo. Why your character doesn't hold on to the clips or magazine is left unanswered though.
* OneHitKill: The pig stick. Many servers ban the pig stick as a result.
* OneManArmy: The Hidden.
* POVCam: Dead or spectating players can patch into the I.R.I.S. team's helmet cameras, watching other players though their perspectives. This can lead to some [[ImpendingDoomPOV feelings of helpless terror if the observing player notices a blur of movement the surviving player doesn't...]]
* RagdollPhysics: ...which leads to some truly macabre sights if the Hidden has been collecting his fallen enemies and pinning them to the ceiling in some sort of Gallery of Death.
* ShoutOut: [[Film/{{Predator}} "If it bleeds, we can kill it!" "He's one ugly mother..."]] Hell, between the Hidden's ability to pin corpses to ceilings and walls and his invisibility, the entire game is basically an homage to ''Film/{{Predator}}'', just with less lasers and more knives.
** Although the game's basic plot and play seems a ShoutOut to ''Hollow Man'' as well.
* SlasherMovie: Except you're not watching it, you're ''playing'' it.
* SprintMeter: The Hidden uses a system akin to this to fuel his WallCrawl, AuraVision and long jump abilities.
* StandardStatusEffect: The "Less Lethal" combines slowing, dizziness and poison in one shot - although, as the name suggests, the poison can't kill anybody outright.
* StealthBasedGame: For the Hidden, anyway.
* SurvivalHorror: ''Oh yeah.'' The I.R.I.S. players have limited ammo and no way to recover health. Best of all, dead teammates are unable to communicate through text or headphones, so if you wander around by yourself for a while and ask your squad to report in, you may feel very lonely...
* SuperStrength: The Hidden. Not in the usual MegatonPunch way, but he can lift and throw corpses, crates, bedframes and Xboxes with enough force to kill.
* TenLittleMurderVictims: The Hidden is dangerous but not immune to bullets, so his best bet is to try to pick off the other players one by one.
* TenSecondFlashlight: Thankfully averted.
* VisibleInvisibility: Although not nearly as noticeable as other examples, the Hidden can be seen as a faint flicker if you have very good vision. Also, when ''you'' play as the Hidden, you can see your own hands, as well as your weapon.
* WallCrawl: Well, wall ''cling,'' but it works just as well.
* WithGreatPowerComesGreatInsanity: Either that, or Subject 617 is really pissed about his DNA being run through a blender.