In this thrilling story, a renowned assassin named Hyung Wook suffers an accident in a public sauna, resulting in amnesia. At the same time, Jae Sung, an aspiring actor down on his luck, seizes the opportunity and switches locker keys with the unconscious Hyung Wook. To his surprise, the key leads him to a lavish condominium, filled with the wealth and secrets of a successful hitman. Struggling with his memory loss, Hyung Wook awakens to find himself in a dire financial situation, indicated by outstanding payment bills. With the help of a paramedic, he tracks down his supposed residence, only to discover that he is, in fact, a destitute actor named Jae Sung. In a twist of fate, Hyung Wook attempts to piece together his forgotten identity while pretending to be Jae Sung. Unexpectedly, his muscle memory from his former life as an assassin aids him in becoming the newest on-screen action hero. Through the rigorous filming of intense action sequences, Hyung Wook's memories gradually resurface, leading to a captivating journey of self-discovery.