Sarah Walker is the alias of one of the main characters of the fictional television show Chuck on NBC. She is portrayed by Yvonne Strahovski and is one of two agents assigned by the NSA and CIA to protect Chuck Bartowski after he accidentally downloads the secret government computer known as the Intersect into his brain. Sarah's spy partner is the one and only John Casey.

Biography
Very little information about Sarah's past has been revealed so far. The only person outside of her family confirmed to know her real name (via her birth certificate) is Director Graham,[1] and it is otherwise only known for certain her middle name is Lisa. Her father was a con artist and much of her youth was spent moving from city to city as part of his ongoing schemes. Among the aliases she used as a child were Katie O'Connell and Rebecca Franco. She attended at least her senior year of high school—and graduated in 1998—under the alias of Jenny Burton.[1] While playing "Know Ya!" at the beginning of "Chuck vs. the Wookie," she mentions having a sister; however, it is currently unknown whether this is true or part of the identity she created as part of her cover. Nothing has been revealed about Sarah's mother, except that she presumably left Sarah and her father at a young age.

Recent episodes have revealed that as a child growing up, Sarah was not only aware of her father's activities, but actively participated in them. One of their scams involved Sarah fooling an armoured car driver into thinking she'd been hit by the vehicle while riding her bike, while her father claimed to be a doctor and examined her. During the confusion, he would then lift money from the vehicle. Another trick was the "Lichtenstein," in which her father would masquerade as a struggling German inventor or businessman attempting to unload an invention or other valuable commodity that never actually existed. Christmases were spent scamming the Salvation Army.

Sometime around 1998, Sarah's father was arrested for his own protection after a scam went wrong and put his life in danger. He left her a hidden cache of money for just such an emergency, and it was while recovering this that she was first approached by CIA director Graham. He took her in as a protege after remarking on her many aliases as a child and gave her the cover name of Sarah Walker. Although apparently 'recruited' at this point, flashbacks make it clear that she continued in high school; several of the popular children cruelly mocked her as the 'jailbird's daughter' because of her father's imprisonment.[1] Although tacitly recruited by Graham before finishing high school, Sarah was officially brought into the CIA out of college, which she attended at Harvard University.

Beginning sometime between 2003 and the present day, Sarah was partnered with Chuck's former friend and college room mate Bryce Larkin. Their professional relationship eventually evolved into an intimate one. When Bryce apparently went rogue to steal the Intersect computer—not realizing that he did so to protect it from a hostile government cabal known only as Fulcrum—Sarah felt both personally and professionally betrayed.

Sarah was subsequently assigned by Graham to attempt to recover the Intersect. The only lead was the e-mail Bryce sent to Chuck, and she tracked him down to the Buy More where, posing as a customer with a broken phone, she first made contact.