Erza Scarlet, Fairy Tail's strongest female wizard and disciplinarian, returns to the guild after an extended absence. To the guild's shock, Erza recruits Natsu and Gray to help her stop the dark guild Eisenwald from retrieving Lullaby, a demon flute that kills all who hear its music; the guild's administrator, Mirajane Strauss, implores Lucy to keep Natsu and Gray from fighting and angering Erza. Arriving at the town of Onibas, Natsu is accidentally left on the train and assaulted by Kageyama, a shadow wizard from Eisenwald. Unable to fight back due to his motion sickness, Natsu catches a glimpse of Lullaby before his friends rescue him. Kageyama delivers Lullaby to Eisenwald's leader, Erigor, who plans to use the flute as part of an assassination plot.