When Republic City Police capture the mysterious and powerful Y/N after a devastating battle, Chief Toph Beifong calls an emergency meeting with Avatar Aang, Fire Lord Zuko, Katara, and Sokka to determine who—or what—they’ve imprisoned. With no known past, no reliable records, and countless conflicting eyewitness accounts of Y/N’s abilities, the group struggles to uncover the truth behind the enigmatic prisoner. As unanswered questions pile up and Y/N remains eerily calm within their reinforced cell, Team Avatar begins to realize that their newest captive may be connected to a much larger mystery—one that could threaten the peace they fought so hard to achieve.