How does Stevenson present mystery in chapter 4

Nearly a year later, a respected member of London society, Sir Danvers Carew, is murdered. A maid sitting by her window in the very early morning hours witnesses the story recounts the event. She gazes out her window, romantically feeling at one with the world, when she sees an aged man with white hair walking along a nearby path. She watches as he meets another, smaller man, whom she recognizes as Mr. Hyde. Suddenly, Mr. Hyde brakes out in anger and attacks the white haired man, beating him to death with a cane. The maid faints upon witnessing such horror.