Season 1

A man named "M" invites seven people to a murder game party. Among the eight in the room, one will become a victim, and another the culprit.

Recognized for their performance, the detectives report to Jeju Island, where their first client asks them to participate in a treasure hunt.

Jong-min comes across a diary of a dead teen girl who was possibly murdered. To find the truth, he gathers the detectives at the school she attended.

A woman turns up dead on an island off the coast of Incheon. The detectives learn that a centuries-old legend of a vampire has haunted the islanders.

Without any cases to solve, the detectives enjoy watching a magic show rehearsal -- until the show's star magician suddenly disappears without a trace.

A man who introduces himself as K's old friend offers the detectives lavish pay and a chance to partake in a special mission -- but there's a catch.

A culprit asks specifically for the detectives to escort him to the police station. In exchange, he promises to tell them everything they want to know.

The detectives receive a text message from K that was written three months ago. It asks them to come to Incheon, where their final test awaits.