Theme of duality is as old as human civilization. Every coin has two aspects, every human being has white and black shadows in his/her personality. Stevenson has presented this age-old theme in the form of a gripping thriller. Dr. Henry Jekyll, a sober, charming intellectual and his alter-ego Mr. Hyde, an in human, uncivilized brute. Stevenson has been very convincing in the explanation of this very negative side of otherwise a very social human being. His argument is that basically man is still a caveman at heart. Social etiquettes, laws, rules and regulations are artificial and to a great degree imposed upon. Generally human beings like to maintain status-quo and also care a lot for their social-repute or image. The same thing becomes bane for Dr. Henry Jekyll. One part of his nature loves to indulge in the sensual and the forbidden. Second part craves for social recognition. The supreme science of Chemistry provides an escape route to his inhibitions and with 'her' help he starts enjoying a life sans morals, values or even humanity. But this life's debauchery leads to two deadly encounters with law of the land. Mr. Hyde's night excursions put Dr. Jekyll's day-light existence into jeopardy. Dr. Jekyll realizes too late his own stupidity. His drug induced change of personality into Mr. Hyde becomes an evolution process. More Dr. Jekyll indulges in his fantasy, more powerful Mr. Hyde becomes. Things lead to a point where drug is no longer needed; after a set time duration Dr. Jekyll automatically changes into Mr. Hyde. Now he needs drugs to get back to original Dr.
Jekyll. To his horror, Dr. Jekyll realizes that Hyde has no interest in Dr. Jekyll's existence. For him Dr. Jekyll is only a shelter, a safe place from legal forces. Crisis gets maximized when stock of chemical salt used for this conversion gets exhausted. Entire London gets ransacked by Dr. Jekyll, but same salt cannot be retrieved. On top of it he keeps metamorphosing into Mr. Hyde. With the intake of last dose, he realizes the end of Dr. Jekyll has come, now he won't be able to change into Dr. Jekyll again ever. So he confesses everything in a letter to his very close friend and lawyer Utterson. Utterson, on the other hand, has been trying for a long time to unearth the relation between Dr. Jekyll and Mr. Hyde. When Dr. Jekyll has shut himself in his lab and has been raving mad to get the right salt, his butler Poole becomes suspicious. He and other servants listen to Dr. Jekyll's voice and footsteps carefully and reaches to the conclusion that Hyde has murdered Dr. Jekyll and is now trying to escape somehow. They call Utterson and together force the door of the lab open. Hyde consumes poison and dies. Dr. Jekyll is nowhere to be found. Utterson finds Dr. Jekyll's last letter and the entire mystery gets solved.