Mushitaro Oguri is the man suspected of being involved in both Dostoyevsky's orchestration of Kunikida's imprisonment, and the murder of a mystery author that has sparked public uproar.

Ranpo is forced to struggle like never before against insects manipulated by Mushitaro, who has the Ability to erase all evidence, "The Perfect Crime" - but meanwhile...!

Dazai is arrested, the mysterious organisation "The Decay of Angels" pulls strings behind the scenes, and high-ranking government officials are suddenly abducted...

As the deepening darkness closes in, the Armed Detective Agency faces a crisis that threatens its very survival!