Despite joining the Armed Detective Agency, Nakajima lacks conviction that he'd be of any use. Just as he's about to bid the agency farewell, a bomber takes over the agency with one of the agency employees as his hostage...!

Though saved from the Port Mafia by Dazai's intervention, Atsushi feels responsible for bringing trouble to the Agency's door. Rather than risk another attack because of him, Atsushi decides to leave the Agency and makes a call to the Port Mafia...

The Agency investigates a series of disappearances in Yokohama. Kunikida enlists the help of a hacker named Taguchi Rokuzou, but all they find are photos of the victims and mention of a mysterious figure called the Azure Messenger. They follow the trail of clues to an abandoned hospital...

Mori, the leader of the Port Mafia, sends a letter to Margaret M. and Nathaniel H., threatening to destroy them and the ship they are protecting.

Atsushi is abducted onto the Moby Dick. Meanwhile, Lovecraft succeeds in capturing Q. Francis F. and the Guild prepare to carry out what they call their "emergency plan."