Chuck Versus the Mask

That night, Chuck and Hannah watch the gala from the control room, while Shaw and Sarah attend as a couple in order to make their way into the vault and swap the mask for a duplicate.

However, Chuck flashes on a Ring operative named Nicos Vassilis, and leaves Hannah alone to warn Shaw and Sarah.

Back at Castle, Sarah and Shaw inadvertently trigger the weapon, which fills the lab with a chemical identified as cyclosarin and forces a lockdown to prevent further outbreak.

Chuck arrives to update Shaw and Sarah only to find them trapped, and flashes on the gas's chemical composition and discovers that there is a counter agent that will reverse the effects if used within an hour.

To force Vassilis to give them the counter agent as well as release Hannah, they rig it with a smoke grenade to simulate the effects of the gas.

Chuck flashes on the correct vase, smashes it over Vassilis's head, and gives the counter agent to Casey while he frees Hannah from the vault.

Shaw begins hitting on Sarah, first by bringing her coffee and a swizzle stick, noticing that she chews on them, and later at the party by making advances, ostensibly for cover.

Later that night, Ellie meets him at the Buy More where they attempt to corner Chuck and force him to come clean but instead find him making out with Hannah.

House of the Book, located on the Brandeis-Bardin Institute campus in Simi Valley, California, was used as the exterior of the museum.

On February 9, 2010, Josh Schwartz and Chris Fedak directly addressed the controversy through an interview with television critic Alan Sepinwall.

Schwartz and Fedak acknowledged the strong fan involvement in the show, but defended the events of the episode as an important part in the ongoing development of the main storyline and the relationships of the characters.

Schwartz also noted he appreciated seeing the reaction the episode generated, citing it as a sign of viewers' investment in the show and the characters.

[4] Maureen Ryan of the Chicago Tribune found some fault in several plot holes within the episode, but also supported the direction of Fedak and Schwartz, citing both the Sepinwall interview and Holmes' analysis of the fan reaction.