Dr. Isaac Kleiner was a renowned quantum physicist known for his work on teleportation. He gained significant recognition in his field, appeared on magazine covers, and worked as a lecturer at MIT, where he met Gordon Freeman, then a Ph.D. candidate. Impressed by Gordon’s shared interest in teleportation, Kleiner formed a close friendship with him. Later, Kleiner joined the Anomalous Materials team in Sector C of the Black Mesa Research Facility, overseen by Wallace Breen. The team studied exotic materials from the alien world Xen. There, Kleiner befriended fellow scientist Eli Vance and security guard Barney Calhoun, and grew close to Eli’s family—his wife Azian and daughter Alyx, who affectionately called him “Uncle Kleiner.” However, he developed a rivalry with Dr. Arne Magnusson over research funding. Kleiner later recommended Gordon for a position at Black Mesa, helping him secure the job over another candidate, Judith Mossman. In addition to research, Kleiner handled administrative duties and was scheduled to instruct hazardous materials training. Despite his brilliance, he was absent-minded, often locking himself out of his lab after forgetting his keycard. When the Resonance Cascade triggered the Black Mesa Incident, Kleiner survived and later witnessed the Combine invasion and humanity’s defeat in the Seven Hour War. He reunited with Eli, Magnusson, and Barney to form the Resistance against the Combine. The group relocated to City 17. During their journey, Eli lost his left leg while helping Kleiner escape a Bullsquid attack. Judith Mossman eventually joined them. In City 17, Kleiner established a hidden lab beneath an abandoned building, while Barney infiltrated Civil Protection as a spy. Kleiner continued developing teleportation technology, creating a teleporter linked to Eli’s lab at Black Mesa East to smuggle people safely out of the city. He also researched headcrabs, discovering how they zombified hosts by piercing the skull. After removing the organ from one specimen, he kept the now-harmless creature as a pet named Lamarr, after Hedy Lamarr. During this time, he also developed the upgraded Mark V HEV Suit.
