The story centers on a London lawyer named Gabriel John Utterson, who investigates strange occurrences between his old friend, Dr. Henry Jekyll and the evil Edward Hyde. The work is commonly associated with the rare mental condition often called "split personality" where, within the same body, there exists more than one distinct personality. The work is frequently interpreted as an examination of the duality of human nature, usually expressed as an inner struggle between good and evil. It has also been noted as "one of the best guidebooks of the Victorian era" because of its piercing description of the fundamental dichotomy of the 19th century "outward respectability and inward lust," as this period had a tendency for social hypocrisy.