The book "The Strange Case of Dr. Jekyll and Mr. Hyde", by Robert Louis Stevenson gives weight to the argument that evil will always corrupt and destroy good. Dr. Jekyll, through his otherworldly experiments, discovers a way to separate his benevolent and malicious sides into two separate entities. In the course of doing this, Mr. Hyde, the physical representation of all that is twisted within him, begins to gain more of an anchor within the real world than Henry Jekyll has.
Jekyll first began indulging in his concoction in order to live a carefree lifestyle. He could fulfill his deepest, darkest desires as Mr. Hyde without fear of tainting his own good name. Every time he drank of his tincture, his body would undergo gross changes, malshaping his face and shrinking his body noticeably. Mr. Hyde had a smaller stature, Jekyll infers, because of the lack of time he had devoted to nurturing his darker half during the course of his life. When Jekyll became Hyde, he could indulge in all the naughty, sinful pleasures of the flesh and mind that Jekyll would never dream of partaking in. The reader can infer that Jekyll slowly but gradually grew addicted to this carefree lifestyle he could lead. Slowly but surely, Jekyll's noble, upstanding self began to give way to his Hyde. Jekyll, the representation of all that was good within him was, at this point, corrupted and tainted beyond repair by Hyde's black grip and cold fingers.
One morning, Jekyll awoke to find that ridding himself of Hyde was no longer as simple as downing another flask of his magic elixir. Hyde was slowing starting to inflict his features upon Jekyll little by little. Now that he would slip into pseudo-Hyde mode every time he dozed off, he could no longer leave his residence or venture out upon the streets. Surviving on the last of his potion, Jekyll penned a confession, resigning to the fact that he could no longer suppress Hyde and could only hope that he had the courage and strength to put an end to both of them. Hyde had overcome and won the day and thus destroyed the last bastion of good within that body. Evil had not only triumphed over good, but tore at it's very foundation and hounded it until nothing of it was left.
Evil is a strange thing. It grows and festers in the recesses of every human mind, subsisting off the little dirty secrets we refuse to admit even to ourselves. If one cannot learn to understand and embrace their dark nature, then one is destined to be controlled by it. Henry Jekyll learned this lesson the hard way, but we all have to face our Hydes' at one point in our lives, and just like Henry, it may just be too much.