Dr. Jonas Zarnow is the top scientist brought in by Sarah and Casey to retrieve the secrets from Chuck's brain in "Chuck Versus the Helicopter". He is one of the NSA's top scientists. He is portrayed by John Fleck.
Chuck is codenamed "Patient X" and is hidden behind a theater room at the Buy More and Zarnow is restricted from meeting him for the sake of keeping Chuck's identity a secret. He then sends several images and only one encoded subliminal image as a test to prove that Patient X has the Intersect.
However, after he fakes his death with a car bomb, it is revealed that his loyalties lie elsewhere. He kidnaps Sarah with the intention of torturing her to determine the identity of the human Intersect. After a struggle in a helicopter, Chuck is able to capture Zarnow. He has been charged with feeding America's secrets to North Korean intelligence, among other crimes.
He is said to have aided in the creation of the Intersect. It is unknown if he has met Stephen Bartowski (codenamed Orion) or Howard Busgang (codenamed Perseus) during his time in designing it. His government codename has never been revealed or mentioned.
- Whilst the term/concept was not employed at this stage in the series, it must be considered at least possible that he is a Fulcrum agent, or even part of The Ring.