In 1885, Robert Louis Stevenson had a vivid dream about one man transforming into another, which was interrupted when his wife woke him up. 
 That dream inspired "Dr. Jekyll and Mr. Hyde," a haunting novella about a man and his dark alter ego -- and while the big twist is known to everyone (sort of like "Psycho" and the identity of Luke's father), it is a pretty harrowing story. Despite the dry 19th-century prose, Stevenson injects a real sense of looming evil -- a grotesque, malevolent shadow that looms over every scene, even if Mr. Hyde isn't present. 
 The lawyer Mr. Utterson is concerned about a strange person he encountered in the street one day -- the grotesque, cruel Mr. Hyde, who tramples a child and has to be railroaded into paying off the kid's family. What he finds especially troubling is that Mr. Hyde has a connection to his old friend Henry Jekyll. Jekyll pays money to Hyde, and even made a will leaving everything to Hyde if Jekyll should vanish for more than a couple months. 
 Utterson unsurprisingly thinks that Hyde is blackmailing him over some misdeed in his wild youth. So he's determined to save his friend from Hyde. But when Utterson brings up the subject, Jekyll is weirdly defensive of Hyde. 
 A year passes, and a maidservant witnesses an elderly gentleman being clubbed to death by Mr. Hyde -- and Utterson recognizes the murder weapon as a cane he once gave to Jekyll. Jekyll claims to have severed his friendship with Hyde, but his behavior over the following weeks becomes increasingly erratic. When Jekyll's butler begs Utterson to help him save his employer, they uncover the bizarre and grotesque connection between Jekyll and Hyde... 
 "Dr. Jekyll and Mr. Hyde" is one of those stories that is so well known, everyone knows the twist even if they haven't read it. It's even become the shorthand phrase for a person with an evil alter ego, or a split personality. But it was written as a sort of bizarre mystery of sorts -- Stevenson weaves around a bunch of questions about Hyde and Jekyll, which are only explained at the shocking climax.Then we get the final letter from Jekyll, which explains the entire scenario. 
 Interestingly, this novella was the second version of the story. Stevenson originally wrote a different version, then burned it in favor of a more "allegorical" retelling -- the duality of human nature, and the secret underbelly of Victorian society. Jekyll admits to having "pleasures" that society would frown on (probably prostitutes), but he also wants to be the super-respectable doctor whom everyone admires. 
 Stevenson's writing here is a bit dry at times, but the way he writes Hyde is incredibly creepy. He's a dark, grotesque presence even in scenes that he's not in -- an oozing sore that infects everything around him. 
 In Hyde's shadow, it's pretty obvious that something is not kosher with Jekyll. He's a little too respectable and "perfect," except for his weird connection to Hyde. Considering this was Victorian England (where you could do whatever you wanted as long as you were "discreet"), it's obvious he has something horrible going on. Utterson is the flipside of Jekyll/Hyde -- while he's not exactly friendly and outgoing, he's a genuinely good person who wants to help Jekyll. 
 Nobody today will be surprised by the Epic Twist of "Dr. Jekyll and Mr. Hyde," but it remains a very chilling, tragic little novella, and definitely one of Stevenson's best works. A bit dry at times, but a deserving horror classic.