The battle between good and evil is the major theme of Stevenson's novel. Stern acknowledges the battle when he states "Jekyll and Hyde was his first huge selling success in England and America; he wrote it as a shilling shocker, and it became popular at once and ever after as a symbolic portrayal of the dual nature of man, with the moral invested: not to impress us by the victory of good over evil, but he warn us of the strength and ultimate triumph of evil over good once sin is suffered to enter human habitation" (Stern 388). Dr. Jekyll, the protagonist of the novel, is a kind and respected man. His friends, however, cannot understand his companionship with the wicked and mysterious Mr. Hyde, who seems to have come from nowhere and has a terrible hold on Dr. Jekyll. As Hyde commits crimes that shock all of London, nobody can guess how and why the two men are so close to each other. Stevenson uses the dual nature of Dr. Jekyll and Mr. Hyde to convey the conflict of good versus evil in The Strange Case of Dr. Jekyll and Mr. Hyde.
Characters in the novel begin to see the effects of the drugs on Dr. Jekyll and the cause of the of his personality. Dr. Jekyll has a strange appearance due to the effects of the, he begins to changed to Mr. Hyde. The reader is given illusion of two different characters although it is only one person with both good and evil traits. Enfield says, "He is not easy to describe. There is something wrong with his appearance something downright detestable" (Stevenson 5). Soon Mr.Enfield reveals to Utterson that Mr. Hyde has a key to a specific building, which in turn causes him to recall another situation. He says that one time in the middle of the night he saw a small girl and a little man walking perpendicularly at the crossroads of a street. Enfield accounts, "Well, sir, the two ran into one another naturally enough at the corner; and then came the horrible part of the thing; for the man trampled calmly over the child's body".