text: Chuck, Sarah, and Casey all face professional conflicts as they grow to respect each other. A genuine romantic interest develops between Chuck and Sarah. Chuck's desire to maintain his close relationships and eventually return to a normal life is challenged by the dangers and growing responsibilities of his secret life, so that he gradually becomes a more competent, confident, and willing spy. In later seasons, upgrades to the Intersect would include skills in espionage as well as information (the reason the Intersect was originally conceived), giving Chuck temporary knowledge of hand-to-hand combat and other skills such as playing the guitar, using a zipline, foreign languages, dancing, and firearms training.
  In the course of events, Chuck unravels mysteries from his life before the series, often dealing with the Intersect, such as why his parents left, why Bryce got him kicked out of Stanford, and why he is unusually suited for the Intersect. Meanwhile, Casey and Sarah confront unresolved issues from their lives before the series, including their families, Sarah's history with Bryce, and the spies they previously worked with. And as Chuck grows more comfortable with his own role, those closest to him are gradually drawn into his spy life.
  Cast and characters
  Main cast