The Strange Case of Dr. Jekyll and Mr. Hyde is full of mystery and suspense, elements which Robert Louis Stevenson creates through the structure, narrative perspective, and language of the text.
The text is structured so that most chapters end with a cliff-hanger. For example, at the end of chapter 1 the reader is left to wonder as to the identity of the mysterious and devilish Mr. Hyde, and at the end of chapter 3, the reader is left to wonder as to the relationship between this Mr. Hyde and the seemingly respectable Dr. Jekyll. The text is also structured so that the events of the final chapters, chapters 9 and 10, occur before the events described in the previous chapters. Chapters 1 to 8 pose a series of questions to the reader, and chapters 9 and 10 provide the answers to these questions. The suspense of the story would be ruined if Stevenson had ordered all of the chapters chronologically.
For the most part, the story is narrated from the first-person perspective of Mr. Utterson. Mr. Utterson is reliable and sensible, but his perspective is, like any individual's, limited. Mr. Utterson plays the role of detective in the story. Indeed, in chapter 2, Utterson declares, "If he be Mr. Hyde... I shall be Mr. Seek." Readers, following the story through Utterson's limited perspective, adopt the role of detective along with him. Readers are thus as much in the dark as Utterson.
Finally, Stevenson creates mystery and suspense through the language of the text, and through pathetic fallacy, whereby descriptions of the weather reflect the mysterious mood of the story. For example, there is a recurring motif of fog. In chapter 2, Stevenson describes the "fogged city moon," and in chapter 4, he describes the fog which settles upon Soho as "as brown as umber." In chapter 5 the fog is so thick that it seems even to pervade Dr. Jekyll's house, where it "lie(s) thickly" and obscures the light that shines through the "foggy cupola." This frequent description of fog conveys the impression of a city shrouded in mystery. The reader's understanding is increasingly obscured just as the streets and houses of London are increasingly obscured by the thickening fog.