Secretly greatly is a South Korean action-comedy film that tells the story of three North Korean spies who are sent to South Korea to live as ordinary citizens while awaiting orders for their next mission. They pose as a village idiot, a rock musician, and a high school student, but their cover is blown when they are targeted by a North Korean hit squad. As they try to protect their identities and complete their mission, they must confront their own loyalties and the true meaning of friendship.