I had always thought of Henry Jekyll as a good person whose flaws caused him to err and whose inner demons came to light. Isn't that the way the motion pictures portray him, more or less? You sort of feel sorry for him, but not as sympathetically sorry as you feel for Frankenstein's monster. You never feel all that sorry for Jekyll because he is such an arrogant self-righteous vain twit.
But it was my son Nathan who, at a remarkably young age, maybe even just 12 or so, made me realize that the monster was in the mirror all along. Hyde wasn't something hidden inside Jekyll or merely a part of Jekyll, the monster was Jekyll himself. In his own self-righteousness and superiority and elite self-confidence Jekyll, judging and looking down on others, convinced of his own moral worth was the monster. The monster nested in him, yes, because he himself was always the monster.
I can't precisely recall what conversation brought this out, but I think that we were talking about the 1931 Fredric March / Rouben Mamoulian film, one of my all-time favorites. At some point the Hays Office had removed the scene where Jekyll sitting in a park sees a cat attack and kill a bird and Jekyll's rage over it transforms him into Hyde without taking the formula, his final and ultimate transformation. Restored versions of the film have the scene. It reveals Jekyll's hidden hypocrisy that he would be outraged at the death of a bird yet guilty of his own atrocities against his fellow creatures.
But, Nathan pointed out that this is not the scene in the book. In Robert Louis Stevenson's book Jekyll is sitting in the park, yes, but he is judging the people that he sees pass by as shallower and vainer and morally inferior to himself and it is in the midst of his judgmentalism that he transforms fully and finally into Hyde. The point being that he does not become the devil incarnate, in his self-righteousness he was always the devil incarnate.
To quote, "There comes an end to all things; the most capacious measure is filled at last; and this brief condescension to my evil finally destroyed the balance of my soul. And yet I was not alarmed; the fall seemed natural, like a return to the old days before I had made my discovery. It was a fine, clear January day, wet under foot where the frost had melted, but cloudless overhead; and the Regents Park was full of winter chirrupings and sweet with Spring odours. I sat in the sun on a bench; the animal within me licking the chops of memory; the spiritual side a little drowsed, promising subsequent penitence, but not yet moved to begin. After all, I reflected, I was like my neighbours; and then I smiled, comparing myself with other men, comparing my active goodwill with the lazy cruelty of their neglect. And at the very moment of that vainglorious thought, a qualm came over me, a horrid nausea and the most deadly shuddering. These passed away, and left me faint; and then as in its turn the faintness subsided, I began to be aware of a change in the temper of my thoughts, a greater boldness, a contempt of danger, a solution of the bonds of obligation. I looked down; my clothes hung formlessly on my shrunken limbs; the hand that lay on my knee was corded and hairy. I was once more Edward Hyde. A moment before I had been safe of all men's respect, wealthy, beloved - the cloth laying for me in the dining-room at home; and now I was the common quarry of mankind, hunted, houseless, a known murderer, thrall to the gallows."
The Hollywood version interprets Jekyll one of two ways, either he is a nice man with a monster nesting in him or he is a monster with a good man inside him trying to get out. As Hyde eerily shouts in the film, "Free! Free at last!" But in Stevenson's book Jekyll was a monster all along, Hyde is part and parcel of the man himself, and in Jekyll's own self-absorbed vanity he pities himself and fails to see that he judges others not from moral superiority but from a shadow of degradation.
The monster is not within the nesting block nor is the good man, the creature is one flawed and arrogant whole, self-righteously condemning others for petty flaws and vanity while he himself is a murderer unable to see the man in the mirror and condemn his own flaws.