Chuck and Sarah try to become better communicators as they join Ellie and Awesome on a trip to Costa Gravas; a forbidden romance may put Morgan at odds with Col. John Casey.

Chuck, Sarah, Casey and Morgan venture into the jungles of Southeast Asia when The Belgian attempts to unravel the secrets of the Intersect. Meanwhile, Captain Awesome and Ellie try to decipher a secret left behind by her father.

Casey, Chuck and Sarah are sent to Morocco to rescue Roan Montgomery. Morgan plans to meet Alex's mother and Mary spends some time with her family.

Chuck is put in charge of a top-priority mission, but his leadership skills are pushed to the limit when there is a murder in Castle. Meanwhile, Awesome takes on a mission of his own when Ellie finds an alarming new hobby. Elsewhere, Morgan's leadership is also tested when his Buy More troops wage war against Large Mart.

Chuck and Sarah’s wedding prep includes one final detail: ensuring that the mother-of-the-groom makes it to the ceremony alive. Meanwhile, Morgan’s responsibilities as Best Man include his most dangerous mission yet, as he faces Vivian Volkoff. Elsewhere, Ellie tends to the last details of the rehearsal dinner and seeks help from an unlikely source.

Chuck and Sarah track an assassin who is trying to eliminate the new intersect. Morgan tries to adjust to having the intersect. Jeff exposes a new side of himself.

As Chuck and Sarah try to realize a new, safer future, Morgan’s past as the Intersect sends them to Vail on one last mission, where they enlist the help of an unlikely source — the legendary Bo Derek. Elsewhere, Jeff and Lester continue their own spy mission.