He has a note to Cathy from Mrs. Dean and drops it near her secretly so Hareton cant see. Without any consideration of his effort, though, Cathy bluntly asks loudly that it is. Quickly Hareton snatches it, saying that Heathcliff should see everything first before it goes to Cathy. But apparently his conscience speaks up. He eventually lets Cathy have the letter. She reads it but does not give any respond. When asked, she tells Lockwood she cant write back because she has no paper. Heathcliff has destroyed all her books she cant even rip a page. Then she begins to make fun of Hareton because shes seen her books with him while he cant even read.
Hareton gets mad at this. And its probably the last straw because he adds hes not going to try to learn anymore.
When Heathcliff returns, Lockwood tells him what he came there for in the first place. Heathcliff thinks hes only trying to put off paying the rent, which makes Lockwood mad.