In Dr. Jekyll and Mr. Hyde, how does Robert Louis Stevenson create and continue a sense of suspense and intrigue?

Stevenson introduces
the fiendish character of Mr. Hyde but does not reveal who he is or how he is connected to the
esteemed Dr. Jekyll until the end of the book. At the outset, Mr. Utterson, Dr. Jekyll's lawyer,
merely hears of the dastardly deeds of Mr. Hyde and then learns that his old friend Dr. Jekyll
has bequeathed everything to Mr. Hyde in his will. Even more mysteriously, Dr. Jekyll leaves
instructions that everything is to be left to Mr. Hyde in the case of his disappearance, which
adds an extra layer of suspense. It is unclear why Dr. Jekyll would disappear for a length of
time. 

Later, Mr. Utterson comes upon Mr. Hyde leaving Dr. Jekyll's
laboratory, and he finds Hyde distasteful to the point of inducing nausea. However, Dr. Jekyll
refuses to tell his old friend Utterson why he continues to befriend Hyde and wants to leave him
his possessions in his will. To heighten the suspense and sense of intrigue, Mr. Hyde is always
surrounded by fog, and Mr. Utterson comes upon him in...