The leader of the criminal band Oliver falls in with is called Fagin. Often referred to as "the Jew" (revealing Dickens's rampant antisemitism, which was indicative of Victorian society as a whole), Fagin is described as "villainous-looking" with red matted hair and fangs that the author says should belong to vermin. He is a frightening figure, not least because he takes in young homeless children and turns them into criminals.
Oliver is introduced to Fagin by a young boy called Jack Dawkins (infamously known as "the Artful Dodger" or just "Dodger"). Dodger buys Oliver lunch and then invites him back to a house he says is owned by an old man and where Oliver can stay for free. Oliver does not trust Dodger, but with nowhere else to go, he feels he has no choice but to follow him.
Fagin teaches Oliver to pick pockets and then sends him out with Dodger. This proves to be a blessing in disguise. A man catches the gang trying to pick his pocket and calls for help. Dodger and Charley manage to run away, but the police catch Oliver. The man, however, who we come to know as Mr Brownlow, takes pity on Oliver and tells the police that he will take him back to his house.
It is through Mr Brownlow that Oliver finds out the truth about his mother.