The bombs that went off in Castle were made by Volkoff, so the CIA places Vivian Volkoff in charge. When the team goes to meet with her, she gives them a weapon of her father's. The CIA then allows for Alexei Volkoff out of prison for 48 hours to help the team retrieve the other parts of the weapon. Once they find the final piece, Vivian shows up, proving that the whole thing was her plan get all of the pieces to the weapon. Volkoff thinks she's there to save him and rule the world together, but she leaves him to die. No one dies, but Vivian escape with the weapon.
Sarah gives Chuck a prenup and Casey advises Chuck to be cool. Chuck does, which throws Sarah off, so she eventually tears it up. Chuck writes up his own prenup which just says that the two of them promise to love each other forever.
Ellie continues to find more info about the intersect on Orion's computer. Mary attempts to stop her, and then Chuck decides to finally tell her the truth, but backs out when Ellie lies to him about what was on the computer.