It is said that when Melmoth intends to make someone his victim, people can hear strange music around them. Why doesn't Isidora ever hear music whenever he comes to see her? It is explicitly stated that he wanted her to be his victim.
A group of young people in Spain heard the music when Isidora was walking by and Melmoth passed them. Why doesn't Isidora hear it as well?
If Adonijah sold his soul to the devil, how can he terminate his contract of eternal life by writing out Melmoth's history? Why is Adonijah saved, whereas Melmoth is damned and only able to live 150 years?
Why did Melmoth have to murder the priest and get the corpse to conduct the wedding ceremony? Why couldn't he have bribed a living man to do the deed?
Did Melmoth kill Isidora's baby? Why does the baby have a black mark on its neck? Is it due to the bruising or to show it's a demon's child? If Melmoth killed it, was it to make Isidora more miserable so she would sell her soul to the devil?
How did Isidora learn to speak Spanish so fluently when the last Spanish-speaking person she saw died when she was 3 years old?