: Chuck officially trains to become a "real" spy. This season introduces Daniel Shaw (Brandon Routh) as a mentor/rival and sees Chuck and Sarah finally solidify their relationship.

: The focus shifts to family secrets. Chuck and Morgan go rogue to find Mary Bartowski (Chuck's mother, played by Linda Hamilton). The team faces the threat of Alexei Volkoff and Volkoff Industries. Key Guest Stars (Seasons 1-4) Role Notes Alexei Volkoff Timothy Dalton Major Season 4 antagonist Hannah Kristin Kreuk A brief romantic interest for Chuck in Season 3 T.I. Dave Bautista Appeared as a mercenary Roan Montgomery John Larroquette A legendary, albeit washed-up, spy

: Morgan Grimes, Chuck's loyal but often oblivious partner-in-crime. Season Summaries

: Led by CIA Agent Sarah Walker and NSA Major John Casey.

: Ellie Bartowski (Chuck's sister) and her husband, Devon "Captain Awesome" Woodcomb.

: Introduces major lore, including Chuck's father, Stephen Bartowski (played by Scott Bakula). The season culminates in the destruction of the original Intersect and Chuck receiving the upgraded "Intersect 2.0," which grants him physical skills like martial arts.