The fourth season of The Big Bang Theory finds Leonard (Johnny Galecki) falling for Raj's sister Priya following his break-up with Penny (Kaley Cuoco). Meanwhile, Sheldon (Simon Helberg) finds romance with a neurologist who quickly establishes herself as Penny's new best friend. As Howard and Bernadette's relationship blossoms, Bernadette finds herself plagued by Bollywood daydreams starring Raj (Kunal Nayyar).

From the Marvel Universe come the agents of S.H.I.E.L.D., ready to defend the citizens of the world. In the aftermath of the battle between invading aliens and the Earth's mightiest heroes, the Avengers, the special law-enforcement agency S.H.I.E.L.D. begins to intensively recruit new agents to investigate bizarre events and superhuman sightings. Led by Agent Phil Coulson (Clark Gregg), this mismatched team of super spies, geeky scientists, sneaky con artists and regular Joes with extraordinary gifts will have to come together as the first line of defense against the evil forces who seek to corrupt and destroy.