Fagin and Monks, a villainous man, meet in Chapter XXXIX, after Monks has a meeting with Mr. and Mrs. Bumble after the death of old Sally, who, on her deathbed reveals the identity of Oliver's mother. As it turns out, Monks is actually Oliver's older half-brother (his real name is Edward Leeford);when he learns about Oliver's mother and Oliver, he takes the ring and locket that were hers after paying the Bumbles and throws them into the river. When he appears at Fagin's, Nancy is there, too; so, Fagin takes Monks to an upstairs room. But, Nancy sneaks up to the door and listens.
In the next chapter, Nancy goes to a family hotel, the location of which she has overheard from Monks, who mentions Miss Rose Maylie. There, she tells the gentlewoman what she has overheard in the conversation between Monks and Fagin. That is, Monks reveals that he has destroyed the evidence of Oliver's claim to any inheritance and procured the money himself. Further, he tells Fagin that if he re-captures Oliver and makes him into a thief, Fagin will receive a handsome sum of money. Clearly, there is a horrid jealousy of Oliver in Monks as Nancy relates that he mentions,
"...what a game it would have been to have brought down the boast of the father's will, by driving him [Oliver] through every jail in town, and then hauling him up for some capital felony which Fagin could easily manage, after having made a good profit of him besides."
Then he tells Fagin that he would love to "gratify his hatred by taking the boy's life" if he could do so without implicating himself in the murder. But, since he cannot do this, Monks wants to "meet him at every turn in life" and cause Oliver harm. He brags that he can outdo Fagin in evil snares for his "young brother Oliver."