K.C.'s missions get even more challenging as she and her family work to keep their spy life a secret! K.C. goes undercover to infiltrate The Other Side but runs into trouble when someone from her past recognizes her. Ernie undergoes a surprising transformation after he comes into contact with a dangerous serum, and Judy learns more about where she comes from when she meets her creator! And when a former foe needs the Coopers' help, the family has to decide if they can face the consequences of aiding the enemy. Through it all, K.C. and her family know that if they work together it's always mission accomplished!