Mr Hyde and Dr Jekyll are the same person. When he is Dr Jekyll he is living a normal life-like the rest of the people in London, but when he turns into Mr Hyde he is a completely different person. He turns violent and really aggressive.
In chapter 1 at about 3 am Mr Hyde left his house when the London streets were deserted and he sees a girl. Then he goes up towards her and tramples her. Also in Chapter 4 Mr Hyde killed a man called Carew by clubbing him into the earth.

There is also a quote in the story that Mr Hyde lives at the back of Dr Jekyll’s house and in that building there is only two doors ,but there is only one house.
Also Dr Jekyll says the entrance of Mr Hyde’s house is Dr Jekyll’s back door. Mr Utterson and Mr Enfield saw Mr Hyde and Dr Jekyll in one person.

Dr Jekyll and Mr Hyde remind me of the movie Wallace and Gromit the curse of the were rabbit when Wallace turned into a rabbit every night.