In Chapter 1 of Dr. Jekyll and Mr. Hyde, where is the tension created, and how does this intrigue modern readers? Thanks

This
novel begins with a character describing an almost supernatural experience of terror and dread,
followed by the description of random act of violence by a man who shows no remorse.  The
tension results from a lack of understanding.  Why is this door so sinister?  How could a man
just trample a child and not care?  Readers are left feeling uneasy because of this image
unexplaniable human...