In an alternate universe, the Joker dies when an unknown assailant manages to rig his lair with explosives, sealing it tight to ensure he doesn't escape. Harley Quinn found out in the newspaper that the Joker finally croaked. Without the Joker, Harley realised she was finally free to live her life again. So, after some convincing for Arkam Asylum to take her back, she became Harleen Quinzel again, and got her job back as Arkham Asylum's psychiatrist.