In 2017, Son Oh-gong (Lee Seung-gi) and Woo Ma-wang (Cha Seung-won) are in conflict with each other as they look for a true light in a dark world where evil thrives. From there, Son Oh-gong is bound to his protective role towards Jin Seon-mi (Oh Yeon-seo), the little girl he had met years ago. Having made a contract with Seon-mi 25 years ago, entitling her to seek help from Son Oh-gong whenever she calls him in exchange for letting him free, the two meet again in a fateful encounter.