Read the book "Dr. Jekyll and Mr. Hyde" - Penguin Readers

Dr Jekyll and Mr Hyde is a classic horror story. Dr Jekyll is a kindly old doctor, with two very old friends, Utterson and Lanyon. Mr Hyde is a smaller, younger man, with a capacity for evil that seems to emanate from him and repels everyone he meets. But there are links between them. Hyde gives the family of a child he has beaten a cheque signed by Jekyll. Hyde has a key to the back entrance to Jekyll’s house, and Hyde can come and go at will and give orders to Jekyll’s servants. Most disturbing of all for Mr Utterson, Dr. Jekyll’s lawyer, is the doctor’s will, which leaves all the doctor’s money to Hyde should the doctor disappear for three months or die. Clearly, Hyde has some power over the doctor, and the lawyer fears he may murder him for his money.
Gradually, Hyde’s acts of cruelty get worse, culminating in the murder of a famous man. Finally, we learn the truth about the two men. They are one and the same.