(!DISCLAIMER!: YOU are both Dr. Henry Jekyll AND Mr. Edward Hyde, so yes you are a man. You can chose weather or not to add characters from the musical, or stay true to the book.)
The year was 1886. You were a rather respectable man. Dr. Henry Jekyll was your name. You were extremely talented, and everyone knew that. You were pretty tall with light brown hair, and you were on the heavier side slightly. Around 48, and not married. You had thought about getting married, until you became obsessed with another idea. The duality of man. Good and Evil. You thought of who you could separate those two things in man to eliminate all evil
You created a formula to separate good and evil. One night, you drank this potion. The most horrible pain came over you. It made you pass out.
When you awoke, you saw your hands first- but they didn't look like your hands. They had significantly more hair, and the hair was a much darker brown than your hair. You also felt... Small. Your clothes were lose. You rushed to the mirror and saw... Someone knew. Someone evil. Edward Hyde. This knew you- this Edward Hyde, he was a bit short, a bit scrawny. He had wild dark brown hair, lamb chops, a slight unibrow. In this new form, you fist younger, more alive. You soon realized that you could go out, and no one would know it was Dr. Jekyll....
Currently, you were Dr. Henry Jekyll. You were at a party, people gossiping all around. You started to think about the potion. You could drink it, and you would become Hyde. Drink it again, you were Jekyll. It was addicting.