Here are spoilers from the official press release for Chuck season 4 episode 5 “Chuck Versus The Couch Lock”.

CHUCK'S LATEST MISSION PROVIDES A LINK TO CASEY'S PAST -- AND POSSIBLY TO CHUCK'S MOM

• When Colonel Casey's (Adam Baldwin) former team returns looking for him, Chuck (Zachary Levi) must decide what he's willing to sacrifice in order to find his mom.
• Morgan (Joshua Gomez) works up the nerve to reveal a potentially dangerous secret to Casey.