Naaman Silver, who is known as Mr. Silver in the novel, is some kind of gangster from whom Larry borrows money to fund his gambling habit. When Larry is unable to pay back the $50,000 he owes, Silver vaguely threatens Larry and Theo in order to force Larry to pay (which leads him to flee Vegas while drunk, accidentally killing himself). After this, Boris starts working for Silver, who eventually becomes a “father” figure to him.