Chuck, Sarah, Casey and Morgan must stop Dr.Stanley (Robert Englund) from releasing a toxin that induces nightmares... Chuck's mother's allegiances are questioned; Lester and Jeff celebrate Halloween at the Buy More.

Sarah takes dangerous measures to help Mary Bartowski bring down Alexei Volkoff, as Chuck worries that she may be getting in too deep. Sarah, though, must enlist the help of Chuck, Morgan and Casey to complete her undercover mission. Meanwhile, Ellie and Awesome are at odds over what to name the baby.

Chuck encourages Vivian to get in touch with her inner villain for a mission. Morgan's search for a new roommate has unexpected results.

Chuck and Sarah put aside spy work to have a weekend of debauchery, but Awesome’s plans for Chuck’s big night don’t go quite as expected. Meanwhile, Ellie's investigation into her father's computer leads to a life-changing discovery.

Chuck turns to Verbanski for help tracking a computer virus. Lester and Jeff's relationship is complicated by a new Buy More employee.

While Chuck and Sarah contemplate the next step for Carmichael Industries, Casey’s forbidden love, Gertrude Verbanski, walks back into his life with a questionable mission in South Beach. Meanwhile, Jeff’s enhanced intelligence leads he and Lester to suspect that something unusual may be happening at the Buy More.