Chuck and Jill are enjoying the honeymoon stage of their rekindled relationship. However, Chuck's spy life intervenes when Casey and Sarah inform Chuck that he is needed for an immediate mission to recover a list of CIA Fulcrum agents that Guy LaFleur had apparently hidden in his hotel room before being murdered. Jealousy erupts when Jill finally meets Sarah and learns that Chuck and his handler must pose as a couple, especially when she learns that Sarah is posing as a seductively-dressed escort for the mission. Chuck does his best to reassure Jill that his relationship with Sarah is purely business but only finds himself in more trouble when Jill finds Chuck and Sarah in their hotel room in their underwear after trying to wash off a suspected bioweapon. The team recovers a music box in LaFleur's room, which leads them to the opera, where they recover an encrypted flash drive with the Fulcrum list. Chuck and Jill leave for a romantic getaway, during which Jill is kidnapped by Fulcrum and held hostage in exchange for the Fulcrum list. Chuck agrees to the exchange, but first makes a copy of the list with Morgan's Canadian copying device . Chuck and Jill embark on another romantic getaway, during which Sarah and Casey discover from the recovered list that Jill is Fulcrum herself. Meanwhile, corporate efficiency expert Emmett is out to get Chuck and interrogates Morgan to get some dirt on his best friend. Morgan blackmails Emmett with footage of Emmett's drunken stupor.Note The title refers to the phrase "It's not over until the fat lady sings".
