The Tokyo Metropolitan Police Department is sent with an anonymous letter. The message indicates that a suspect in a murder case will attend the countdown party Masquerade Night at Hotel Cortese Tokyo. Detective Kosuke Nitta (Takuya Kimura) must return to the Hotel Cortesia Tokyo undercover. In this location, he meets concierge Naomi Yamagishi (Masami Nagasawa). Without any information about the criminal other than the fact that he or she will be present, Detective Kosuke Nitta frantically searches among the 500 guests for the offender.