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Isaac Kleiner

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This subject is related to the Black Mesa Incident era.
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Kleiner Portrait.jpg
Isaac Kleiner
Biographical information
Alternate names




Function(s) / Belongings
Rank / Occupation


  • Glasses
  • Lab coat
Physical description




Hair color

White (formerly brown), balding

Eye color

Brown (with glasses)

Chronological and political information
Game information
Voiced by

Harry S. Robins

Modeled over
  • scientist01 (HL model)
  • Ted Cohrt (HL2)

Marc Laidlaw



Voice sample(s)

"Oh, fiddlesticks. What now?"
― Isaac Kleiner[src]

Dr. Isaac Kleiner is one of the main characters of Half-Life 2 and its episodes. An archetypal 'absent-minded genius scientist' (although somewhat more benign), he is a prolific author of several works on teleportation and interdimensional travel, and one of the few survivors of the incident that took place in the Black Mesa Research Facility. Later on, he becomes a key (if somewhat self-conscious) leader of the Resistance against the Combine, and a prime member of the Resistance science team.



The second page of L.M.'s letter, where Kleiner is mentioned for the first time.

Kleiner first worked as a professor at MIT, where he was one of the mentors of Gordon Freeman. It appears that the two started their friendship already back then, and that Kleiner was quickly impressed by Freeman.[1] Kleiner would later take employment in the Sector C of the Black Mesa Research Facility, where he worked with Eli Vance and security guard Barney Calhoun.[2]

During this time, Kleiner appears to have become a widely recognized scientist, seeing that he is on the front cover of the magazine Popular Scientist, apparently in an article called "Next level of quantum physics", as well as the author to at least one book, From Here to There in Under a Second, likely about teleportation.[2]

When Freeman showed interest in a job at Black Mesa, Kleiner recommended him for employment in the Civilian Recruitment Division, and this recommendation combined with Freeman's experience at the Institute for Experimental Physics in Innsbruck, Austria,[1] ensured that he got the position instead of his competitor, Judith Mossman.[2] In Black Mesa, Kleiner would also compete for grant money with Arne Magnusson.[3]

A brown-haired Isaac Kleiner on the cover of Popular Scientist. The hair was Photoshopped on a screenshot of his model.

Kleiner appears to have been working with administrative jobs prior to the Black Mesa Incident in Sector C, as he received carbon copies of several letters, from L.M. to other employees, such as his letter regarding Barney Calhoun's new Blue Shift assignment, sent on May 9, 200-,[4] and L.M.'s letter to Colette Green regarding the Xen crystal swap prior to the incident.[5] Kleiner also appeared to be a Hazardous Environment Supervisor or Instructor, as the Hazard Course Training Schedule sent by Gina Cross to Colette Green mentions that Kleiner was slated to instruct Green for a Hazardous Materials Handling on May 9, 200-, although it was postponed to June, and ultimately did not happen due to the Black Mesa Incident.[5] At this time, Kleiner was also on friendly terms with many co-workers, namely Gordon, Eli and Barney, although Richard Keller stated he did not understand what Kleiner was seeing in Freeman.[6]

The Anomalous Materials team before the Black Mesa Incident. Kleiner is the third from the right.

When the Resonance Cascade and resulting Black Mesa Incident occurred, Kleiner managed to escape Black Mesa, although exactly how remains unexplained. Sometime after escaping the facility, Kleiner relocated to City 17, where he formed up the core of the local Resistance along with Eli Vance, Judith Mossman and Barney Calhoun. As Kleiner and Eli entered City 17, however, Eli lost his leg to a Bullsquid while helping Kleiner over a fence.[1][7] In the city, Kleiner set up a small lab beneath an abandoned Northern Petrol building located near the City 17 Trainstation, and began working on teleportation, among other works, while also staying in touch with Eli, who was working in Black Mesa East in the city's outskirts, as well as Mossman, and Eli's daughter Alyx, who was growing up.

Barney worked as a double agent for the local Civil Protection forces at this time, while in the meantime ensuring that Kleiner's Lab would go undiscovered and safe from the Combine. At one point, Kleiner finished his teleport, and tested it with a cat, apparently resulting in its death (which was apparently gruesome enough to mildly traumatize Barney Calhoun), forcing Kleiner to resume work on it. In this time, Kleiner also found a Headcrab, which he de-beaked, making it harmless, and named it Lamarr, before keeping her as a pet and, to an extent, domesticating her, much to the disdain of Barney. When Alyx grew older, Kleiner also worked with her and Barney to rescue Citizens from the Combine, and evacuate them through the Underground Railroad located in the City 17 Canals to Black Mesa East. At the time of Half-Life 2, Kleiner is finishing up his teleport.


Half-Life 2[edit]

Kleiner operating a retinal scanner to open the door to the resurrected teleport.

Along with colleagues (and fellow survivors) Alyx Vance, Eli Vance and Barney Calhoun, he makes up the core of the Resistance against the Combine. Dr. Kleiner has set up a lab in City 17 in an old abandoned warehouse. A teleportation system, developed jointly by Kleiner and Vance, allows for near-instantaneous travel between Kleiner's Lab and Vance's facility, several miles apart. As a pet, Dr. Kleiner keeps a debeaked Headcrab he calls "Lamarr". When Barney informs him that Gordon Freeman has arrived, Kleiner tells Barney to send Gordon his way, forgetting to provide directions. Alyx eventually rescues Gordon and shows him the way to the lab.

Kleiner proclaims that "This is a Red Letter Day" to Alyx, Barney and Gordon.

Kleiner reintroduces Gordon to his HEV Suit which he has upgraded before sending him on his way to safety at Black Mesa East, outside the limits of City 17. Using the recently completed teleport, Kleiner successfully sends Alyx through on its debut. On Gordon's trip however, Lamarr inadvertently interferes and breaks the machinery, teleporting Gordon to several locations before finally rematerializing outside the lab's window behind Dr. Kleiner. With the teleporter damaged and fearing Combine discovery, Kleiner urges Gordon to flee the city on foot. Barney stays to ensure his protection.

As Gordon journeys through City 17's surrounding wasteland, Dr. Kleiner resumes work repairing the teleporter, passing along word to Alyx Vance its near completion once again. As Gordon and Alyx rescue Eli from Nova Prospekt's Depot, Alyx contacts Dr. Kleiner asking if he's ready for an impromptu teleportation, for which he confirms. A rogue Judith Mossman however replaces the lab's coordinates at the last second, and escapes with a confined Eli, causing Alyx to urge a befuddled Kleiner to stop them before realizing her plot. Resetting the Combine portal, Alyx and Gordon safely manage to teleport out of the prison, arriving safely in Kleiner's lab, but over a week later to the utter astonishment and fascination of Dr. Kleiner.

In their absence, the Uprising began, with Barney leading Resistance to make a push towards the Citadel, leaving Dr. Kleiner to fend for himself (and Lamarr) with a shotgun. Days later, Dog turns up to provide greater protection. When Gordon and Alyx teleport in from Nova Prospekt a week into the rebellion, Kleiner is very optimistic about the Resistance's odds and tries to convince Alyx. Alyx escorts Dr. Kleiner to safety, who packs up and brings Lamarr with him, eventually escaping City 17.

A depiction of Kleiner's younger self can also be seen in the lab, appearing on the cover of Popular Scientist, a fictional magazine (and spoof of Popular Science magazine). In it, he sports sideburns and has more hair, which is seen as brown in color. Although this is a somewhat 1970s/80s look, the picture likely dates from around the Black Mesa Incident, thus in the mid to late 1990s. Below the magazine cover is a young Alyx's drawing of him, with the affectionate words 'Uncle Kleiner' on it. A book by Kleiner, From Here to There in Under a Second (likely about teleportation), can also be found in Eli's lab at Black Mesa East.

Half-Life 2: Episode One[edit]

Alyx listening to Kleiner's "Kleinercast".

In Half-Life 2: Episode One Kleiner is not seen in person and is only spoken to directly once in a video transmission with Alyx during the first chapter. However, he is frequently seen during the later chapters on video screens and televisions previously reserved for Breencasts. This message is recorded and looped, simply instructing survivors to make their way to the nearest train station to evacuate City 17. Kleiner also amusingly informs people that the Combine's suppression field is no longer in effect so that "those so inclined should give serious consideration to doing their part for the revival of the species" to which Alyx comments, "is Dr Kleiner really telling everyone to... get busy?". The messages also include some vague information to try and rally people in the face of the fact that the Rebellion is only really beginning and will likely get worse before it gets better. It is likely that all these transmissions are broadcast from White Forest.

Half-Life 2: Episode Two[edit]

Kleiner, Eli and Alyx talking about the Borealis at White Forest.

Kleiner reappears once again in Half-Life 2: Episode Two. First, he is seen beside Dr. Eli Vance and Dr. Arne Magnusson on the first video communication with Alyx and Gordon; he is not seen again until later on when Alyx and Gordon reach White Forest (except during the G-Man's speech). He spends most of his time working with Dr. Magnusson on his rocket. Before the launch, Kleiner briefly notes Magnusson that there is an eight and a half pound anomaly, but Magnusson declares it is within tolerance and the rocket should be fired anyway. Unfortunately for Kleiner, the anomaly was Lamarr who had snuck onto the rocket while the nose cap was open earlier.

Towards the game's ending, when it is discovered that Judith Mossman found the Borealis, Kleiner is enthusiastic about the research contained on the vessel's use against the Combine, but Eli disagrees and states it could be responsible for another disaster on par with the Black Mesa Incident. After the rocket launch, Kleiner remains inside to help Magnusson with destroying the Combine Superportal while Alyx, Eli, Dog and Gordon go outside to see the Superportal dissipate.

Half-Life: Alyx[edit]

Although Kleiner does not appear in person and he is not mentioned by any character, a copy of his book, "From Here to There in Under a Second", can be found in Alyx's Hideout.


Old friends reunite.

Gordon Freeman[edit]

Gordon Freeman was taught by Kleiner at MIT. He then recommended Gordon's position to the administration of Black Mesa, after which they became coworkers. At Black Mesa, Kleiner had apparently a habit of locking himself out of his office and Gordon would race Barney to "break in" to it.[8] Gordon became Kleiner's assistant again as a part of the human Resistance on Earth. He holds Gordon in the highest respects, even though he admits his heroic acts tend to cause trouble.

Barney Calhoun[edit]

Dr. Kleiner probably knew Barney well through Gordon. Barney would often race Gordon into Dr. Kleiner's office via the air ducts to retrieve Kleiner's keys when he locked himself out. Barney would later aid Kleiner in the human Resistance in various ways, though mainly by working undercover in the Civil Protection, keeping the Combine away from his Lab, at no doubt tremendous risk to himself.

Alyx Vance[edit]

Kleiner and Alyx in Kleiner's Lab.

Dr. Kleiner knew Alyx when she was an infant at Black Mesa, and they were close enough for her to call him "Uncle" in a collage she made. In Half-Life 2 they both work together in his lab, and on sending refugees on foot through the canals.

Eli Vance[edit]

Eli is almost the polar opposite to Isaac. He is laid back and confident, whereas Kleiner is reserved, logical, and cautious in most situations. Coincidentally, this is probably why they make such a good team. They have both known each other and worked together since the days of Black Mesa. Kleiner is also affectionately nicknamed "Izzy" by Eli on various occasions.

Arne Magnusson[edit]

While Eli is the opposite to Isaac, Arne is simply headstrong with a very short temper. He has no patience for most of Kleiner's input and at times appears to give him many tedious and long tasks. Back at Black Mesa, the two competed for grant money.

Behind the scenes[edit]

Bust of "Cohrt", Kleiner's original model.
  • Kleiner was first introduced in Gordon Freeman's backstory for Half-Life with the first name "Alex".[9] He was later mentioned in the Half-Life (both PC and PlayStation 2) and Blue Shift manuals, as well as at the start of Decay.
  • Kleiner is voiced by Harry S. Robins, the voice of most of the scientists in the original Half-Life and its expansions.
  • The character's frustrated cry of "Oh, fie!" came from Marc Laidlaw's chemistry teacher who was said to utter the phrase constantly.[10]
  • "Kleiner" is a German surname. Related to "klein", "small" in German, it has several translations, most of the time related to "reduce" or "inferior". "Isaac" is a Hebrew name, and comes from "Yitzchaq", meaning "he laughs".[11] In the Old Testament, Isaac was the son of Abraham, whom God asked to sacrifice to test his faith, though an angel prevented the act at the last moment. As an English Christian name, "Isaac" was occasionally used during the Middle Ages, though it was more common among Jews. It became more widespread after the Protestant Reformation. Kleiner shares his first name with physicist and mathematician Isaac Newton, and the science-fiction writer Isaac Asimov and the late assassinated Israeli Prime Minister Yitzhak Rabin.
  • Kleiner is basically the Half-Life bespectacled scientist model ("scientist01", or "Walter") turned into a real character, as it happened for Walter Bennet. Kleiner's Half-Life 2 appearance was based on Ted Cohrt, an accountant working in the firm above Valve's office. Kleiner's face originally depicted him as much older man (whose model reused elements of the "gas mask Citizen" model),[12][13] but the team changed their mind when they came across Ted Cohrt in an elevator. It is also said that team members sometimes ran into him at Starbucks and the ones who did not know he was Kleiner's face were staring at him, trying to figure out why he looked so familiar.[12] After Cohrt was taken as the model, the older Kleiner face was recycled into the elder Counter-Strike: Source hostage (#4). Although the old Kleiner model has nothing to do with Ted Cohrt, it is named "cohrt.mdl",[13] while the final model, based on Ted Cohrt, is simply called "kleiner.mdl". "Walter" is still used as the name of Kleiner's face texture.
Kleiner in the Episode Two trailer.
  • At the end of the Episode Two trailer released August 2006,[14] Kleiner can be seen in an humorous situation in the rocket silo at White Forest, saying "Mmhh... Now, that's interesting! I think we're getting somewhere!", then screaming when sparks spew from the rocket. This sentence/sequence is not featured in Episode Two; the scream is recycled from the scream Kleiner makes when Gordon appears behind him at the end of the teleportation failure at the start of Half-Life 2.
  • During the development of Episode Two, Marc Laidlaw drew up plans to kill Kleiner at the end of the game when Gabe Newell suggested that Episode Two should conclude with the shocking death of a main character. However, after much discussion, the team decided that Eli Vance would be the victim instead.[15]
  • A new Source 2 model of Kleiner was created during the development of Half-Life: Alyx which went unused when it was decided that Kleiner would not appear in the final game.[16]


  • At the end of the Half-Life 2 chapter Entanglement, Kleiner is shown poking his head through a door in his lab while holding a shotgun in a nod towards the original Half-Life. A scientist at the end of the chapter Lambda Core is shown holding a shotgun in a similar, scared fashion, and is spawned as the scientist model that Dr. Kleiner is based on.
  • Kleiner appears in Dota 2 as an official announcer pack.
  • Kleiner is Marc Laidlaw's favorite character in the Half-Life series.[17]
  • Missing or corrupt sound files in Portal 2 are replaced with a voiceline of Kleiner saying "Oh, fiddlesticks. What now?".


Half-Life and expansions[edit]

Half-Life 2[edit]



Half-Life 2: Episode One[edit]

Half-Life 2: Episode Two[edit]

Half-Life: Alyx[edit]



List of appearances[edit]

Main games[edit]


See also[edit]


  1. The Raising the Bar erroneously identifies this man in the image as Eli Vance. The design of the character matches the description of Kleiner from Marc Laidlaw's vignette Old Friends. In this story, Kleiner is described as a man who wore an eyepatch over his left eye and that side of his face being a mass of twisted scar tissue.[18]


Isaac Kleiner
Combine OverWiki has a list of quotes for Isaac Kleiner.
  1. 1.0 1.1 1.2 Half-Life 2 Prima Guide
  2. 2.0 2.1 2.2 Half-Life 2
  3. Half-Life 2: Episode Two
  4. Half-Life: Blue Shift
  5. 5.0 5.1 Half-Life PlayStation 2 instruction manual
  6. Half-Life: Decay
  7. Half-Life 2: Raising the Bar
  8. Half-Life 2: Episode One
  9. Gordon Freeman on Planet Half-Life (archived)
  10. Twitter favicon.png Tweet: "Karol Kunysz, our chemistry teacher crowned in molecules, is the source of Dr. Kleiner’s “Oh, fie!” He said it constantly." @marc_laidlaw (Marc Laidlaw) on Twitter (November 15, 2021) (archived)
  11. Behind the Name - Isaac
  12. 12.0 12.1 Half-Life 2: Raising the Bar, page 124
  13. 13.0 13.1 Half-Life 2 leak
  14. Half-Life 2: Episode Two Trailer on Combine OverWiki's YouTube channel
  15. The Final Hours of Half-Life: Alyx, Chapter 12
  16. The Final Hours of Half-Life: Alyx, Chapter 8
  17. Marc Laidlaw (Valve) – Interview on (July 17, 2017)
  18. Half-Life 2: Raising the Bar (uncorrected proof), page 360