Polanski made several adaptations to streamline the novel to fit a film format. One major change was omitting the role of the evil Monks Leeford, Oliver's older half-brother. Monks's father had a relationship with Agnes, Oliver's mother, who died while giving birth to Oliver. In the novel, Monks has been taught by his own mother to hate Oliver. It is Monks who pays Fagin to turn Oliver into a criminal, which is why Fagin is glad to keep Oliver around. Monks knows that their father's will leaves the bulk of their father's fortune to Oliver—unless Oliver becomes a criminal. Therefore, besides his motivation of hatred, Monks has a strong financial incentive to turn his half-brother toward a life of crime. The movie also leaves out the story of Rose Maylie, Oliver's pure and beautiful aunt.
In the movie, Oliver is simply left as an orphan, with no other explanation of his background. Fagin and Sikes become his enemies, instead of Monks, and try to kill Oliver in order to silence him.
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