Season 1

Mu-yeom who became a detective for his father, receives news like a nightmare.

Hearing something suspicious about the body of a murder case, Mu-yeom rushes to the crime scene.

It's reported that the first case is the act of Gabdong and there will be a second case of murder.

Mu-yeom is arrested as a criminal, and Yang suggests to compare the DNA of Gabdong and Mu-yeom.

Chief Yang meets Maria and thinks of a girl he met at the scene for a case from a while ago.

Mu-yeom suspects Tae-oh as Gabdong. Tae-oh lets out the story of his dead father to Maria.

The civilians blast anger and attack the police for failing at preventing the fourth case.

Mu-yeom kidnaps Ji-ul and tracks down Tae-oh, with the predicted date for a fifth case approaching.

After finding a corpse, Mu-yeom runs at Tae-oh, and Maria witnesses something shocking.

A phone call rings from the real Gabdong. Mu-yeom finally gets to know the true identity of Gabdong.

Gabdong is finally caught. Mu-yeom starts the interrogation and goes to get his shut mouth talking.

The plane the murder happened at, which Tae-oh was in, makes a flyback.

Tae-oh confesses his crimes, and Maria is shocked after finding out that Gabdong's probably dead.

After finishing the montage, Maria turns the young Gabdong montage into Gabdong of the present.

Mu-yeom and Tae-oh, neither one of them slows down and races to the end of the cliff.

Mu-yeom interrogates to prove Do-hyeok as Gabdong. He gets closer to the secret of the Murder case.

While searching Do-hyeok's house, Mu-yeom finds a suspicious picture frame of the Eiffel Tower.

Tae-oh starts a deal between Do-hyeok and Maria. Mu-yeom notices and makes the two Gabdong gather.

A gunshot rings at the pool Mu-yeom and Do-hyeok are at, and someone falls bleeding.

The trial of the two Gabdong finishes, with hard choices to make, the two fall into a great dilemma.