After being recruited by K, the amateur detectives travel to Jeju Island in order to help a museum director retrieve an artifact that belonged to his deceased friend. With the help of a local news reporter and a tourist from Seoul, they embark on a treasure hunt around the island. Meanwhile, K reveals that, in the past, an error in the chip that was implanted in the detectives had caused them to slowly lose their memories, which led him to abandon Project D. Guests: Ahn Nae-sang, Woo Hyun, Kim Su-ro, Hong Jong-hyun