Lost Between Worlds Alternate Hour 1

After returning home and finding out about an impending apocalypse, Gwynn returns to the human world to meet up with her target, and finish her job, but instead is greeted by the undead! She soon discovers that her ability to claim the souls of the dead is gone, as things seem to keep getting worse. Looking for answers, Gwynn ventures into Mictlan, the underworld. What connection could the undead have with the apocalypse, and what exactly is the cause of it?