Cole escapes after being tortured by Fulcrum and returns to Castle. Sarah and Casey are assigned to hunt down a scientist code-named Perseus, who is the mastermind behind Fulcrum's plans to build their own Intersect. They fail to retrieve Perseus but escape Fulcrum's capture after a less-than-graceful rescue by Chuck and Cole. After locating the lab of Perseus, Chuck learns that a man code-named Orion is the designer of the Intersect and headed the entire Intersect project. Sarah wrestles with her feelings for Cole and Chuck, ultimately choosing Chuck. Morgan tries to talk Anna out of moving in with him after previously agreeing to move in with Chuck, but later decides that living with Anna is what he truly wants.Note The title refers to the fact that Chuck is given a gun on a mission for the first time.