When The Organization assigns Junior Spy of the Year, Brett Willis, to go undercover as K.C.'s boyfriend for a mission, K.C. winds up having real feelings for him. Meanwhile, Craig and Kira receive alarming news that their old arch rival Zane is back and determined to destroy them.

Zane has captured K.C., but her family has no idea because the evil agent has created a K.C. look alike to take her place and defeat the Cooper family.

The K.C. doppelgänger gains access to The Organization, now Kira and Craig must race against the clock to save their daughter and the agency.

K.C. goes even deeper undercover into The Other Side’s training ground and is close to getting the intel she needs, when she discovers Brett is her new training officer.

Brett is back and his assignment is to eliminate K.C.! But when he can’t bring himself to complete his mission, K.C. decides to help protect him from The Other Side.

When K.C. enlists her family to help Brett escape from The Other Side, the Coopers find themselves in danger with enemy agents and The Organization.