Mort doesn't quite fit in with his family or anywhere else, so his father takes him to a hiring fair, hoping that someone will take him on as an apprentice. Surprisingly, Death arrives and offers Mort the chance to learn his trade guiding souls to the afterlife. Mort accepts and begins his unusual apprenticeship. As Mort adjusts to his eerie new job, he encounters Princess Keli, whose death he is supposed to oversee. But Mort defies fate and prevents her assassination, thereby upsetting the balance of reality. Chaos begins to unfold as the world tries to correct itself. Meanwhile, Mort begins to take on more characteristics of Death himself, while Death starts exploring what it means to be human, even taking a brief holiday. Mort must ultimately confront the consequences of his actions and restore balance, all while navigating the complexities of love, identity, and destiny.