Utterson is a typical Victorian man who tries to help everyone "inclined to help rather than to reprove"
Stevenson may be using Utterson's desire to solve the mystery to suggest everyone has a darker side to them, perhaps Utterson feels a connection to Hyde encouraging him to solve the mystery
dual nature of man
""Satan'ssignature" is written upon Hyde's face
He abuses Hyde suggesting he has been stabbed by the devil in the face and is the physical identity of the devil
religion
"I inclined to Cain's heresy...I let my brother go to the devil in his own way"-foreshadows the epistolary text as Utterson watches Jekyll lose himself and become obsessed with his darker side