It is believed that Death chose Mort partly because Death himself had the nickname Mort (he is called this by the other members of the 4 horsemen) This is some sort of Mortality = Mortimer joke. Can you tell that Death is making the joke?
The pressure of the job forces Mort to make a few mistakes, but like all good heros, he grows some spine, gains some self control, challenges death to a duel and waltzes away with the girl...
He marries Deaths adopted daughter Ysabell and they live relatively happily ever after as the duke and duchess of sto helit.
Pity "happily ever after" is only about another 15 years...
They are however survived by a daughter, Susan Sto-Helit who should really be named Susan Death. But that's another book... [Soul Music]? to be precise