A perplexing photo containing a disturbing message surfaces. The police consider the possibility of the culprit being one of their own.

Si-mok turns his attention to an unusual case involving the sudden death of a former prosecutor, and finds that nothing quite adds up.

Taken off the case, Si-mok and Yeo-jin return to their work on the police-prosecutor council. Tae-ha and Bit head to a sensitive meeting together.

While getting to the truth about the night of the attorney's death, Si-mok and Yeo-jin learn about the involvement of a mystery person.