As a teenager, Mort had a personality and temperament that made him rather unsuited to the family farming business. Mort's father, named Lezek, felt that Mort thought too much, which prevented him from achieving anything practical. Thus, Lezek took him to a local hiring fair, hoping that Mort would land an apprenticeship with some tradesman; not only would this provide a job for his son, but it would also make his son's propensity towards thinking someone else's problem.At the job fair, Mort at first has no luck attracting the interest of an employer. Then, just before the stroke of midnight, a man concealed in a black cloak arrives on a white horse. He says he is looking for a young man to assist him in his work and selects Mort for the job. The man turns out to be Death, and Mort is given an apprenticeship in ushering souls into the next world (though his father thinks he's been apprenticed to an undertaker).
When it is a princess' time to die (according to a preconceived reality), Mort, instead of ushering her soul, saves her from death, dramatically altering a part of the Discworld's reality. However, the princess, for whom Mort has a developing infatuation, does not have long to live, and he must try to save her, once again, from a seemingly unstoppable death. Both the princess and Mort end up consulting the local wizard, Igneous Cutwell, for various methods of assistance with the crisis.
As Mort begins to do most of Death's "Duty", he loses some of his former character traits, and essentially starts to become more like Death himself. Death, in turn, yearns to relish what being human is truly like and travels to Ankh-Morpork to indulge in new experiences and attempt to feel real human emotion. Conclusively, Mort must duel Death for Mort's freedom. Though Death wins the duel, he spares Mort's life and sends him back to the Disc.
The princess is saved from a second death when the alternate reality Mort created is reduced to a pearl-like state. This pearl is given to Mort for safe-keeping. At the end of the novel, Mort marries Ysabell, Death's adopted daughter.
