Book review --The last Sherlock Holmes story

This story is about the detective,Sherlock Holmes and his friend Dr watson .They found a strange murder case in London.The murder killed the woman and after he kill her.He cut the woman's body into pieces.Then the muederer do it against and against.And at the last time of the murder.Dr watson saw the muederer was his best friend,Holmes.And Dr watson found Holmes had too much cocaine.And then he had dual personality.And then Holmes bring him to waterfall.And he want to shoot watson but watson said that were friends don't make yourself a murderer.sadently,Holmes go back to his character.And then he know things.He do it wrong so he jump down from waterfall.At last,Dr watson think he don't want his friend evil side,to let other people known so he keep the secret forever.