Sean Cassidy is discovered by the villainous Changeling, who invites him to join Factor Three. Cassidy declines upon learning Factor Three's goals. Factor Three, along with the Ogre, captures him and places a headband containing explosives around his head to force him to obey their commands. Codenamed after the banshee, a spirit from Irish mythology, Cassidy is forced to perform various criminal missions for Factor Three. On a mission in New York City, Banshee encounters the X-Men. Professor X uses his telepathy to disarm the headband and remove it, allowing Banshee to help the X-Men defeat Factor Three.