A man named M invites seven people to a murder game party hosted by his boss, known as K. As soon as the game begins, M is shot by an unknown perpetrator, which turns the game into a real crime scene. They soon realize that the murder is related to an operation called Project D, in which they are also involved in. Using the tarot cards given by a gypsy as their clues, the seven witnesses must attempt to find the culprit before it reaches the next victim. Written by Wikipedia

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. Written by Wikipedia

While on a vacation in Jeju Island, Kwang-Soo wakes up with a hangover and finds a dead woman in his room. Fearing that the police will brand him as a suspect, he flees the scene and decides to find the murderer himself. The six other detectives receive a call from K, saying that Kwang-Soo has become a murder suspect. This leads them to investigate the case in an effort to prove his innocence, or else they would have to arrest him. Written by Wikipedia

Jong-min encounters a child who gives him the diary of a teen girl. He finds out that the girl had recently died at Songdo Central Park under mysterious circumstances and receives a call from K, who tells him to gather the detectives at the high school where she attended to look into her death. During the investigation, the detectives discover that her friends have been receiving text messages from her even after she died. Written by Wikipedia

An ex-criminal, whom Jae-Wook had arrested during his days as an agent, tells him that a woman was murdered in his hometown, a small island near Incheon. When the detectives go to the island, they discover that the residents believe that a vampire lives in the island and kills a woman whenever anyone tries to investigate on the murders happening in the village. Meanwhile, K tells them that one of the doctors involved in Project D was from the same island. Written by Wikipedia

Two rival curators of an art museum enlist the help of K's detectives and the Genius Detective Team in an attempt to outshine each other. The competition between the two teams becomes fierce as they must find the self-portrait of a recently deceased artist before the painting is auctioned off on the same night. Written by Wikipedia

The detectives attend a magic show rehearsal to support Sehun, who would be opening the show with a dance performance. During the rehearsal, the magician mysteriously disappears while performing one of his tricks, which sends the crew in a panic as the show would be happening in a few hours. As a result, the director asks the detectives to find him before the show begins. Written by Wikipedia

A man claiming to be K's old friend challenges the detectives to solve a 20-year-old case through a series of tests in order to measure their skills in criminal investigation. Each test has a different goal, and the first detective to complete a test is rewarded with a large sum of money. The man also promises to provide the pass code for the box that the detectives had obtained in Jeju Island, which contains valuable information about Project D. Outside the mission, Se-Jeong is seen leaving flowers for M at a columbarium. Written by Wikipedia

Yeon-Seok turns himself in and requests that K's detectives should be the one to transport him to prison. Although this confuses the detectives, they accept his request in exchange for information about Project D and his involvement with it. While on their way to prison, Jae-Suk receives a phone call from an unknown man demanding Yeon-Seok to be brought to him, or else, a bomb that he planted onto a stranger's bag will be detonated. Written by Wikipedia

The detectives receive a scheduled message from K that was written three months ago, during the planning of the murder game party. He tells them that a final test for them is waiting at a safe house in Incheon. However, they also receive a message from a familiar voice saying that he has kidnapped K. Written by Wikipedia