In Chapters 15 & 16, How does the tone affect the reader's interpretation of the story?

Chapter 15 contains the tone of violence even as Biddy teaches Pip and Pip teaches Joe.In this chapter, Pip is witness to a fight between Orlick and Joe, apparently egged on by Mrs. Joe, reminiscent of Estella complimenting with a kiss Pip's fight with the pale young gentleman. Violence comes quickly and rather unexpectedly throughout the novel and, as in this case, does little to solve anything.The tone is suddenly dark and contains some foreshadowing. Chapter 16 continues in this way. Pip's helping the convict continues to have a shadowy tone. Dickens subtly changes how we view Mrs. Joe by referring to her now as "my sister." Pip's relationship with his sister sours as well. Before the accident, the readers almost forget the blood relationship between Pip and Mrs. Joe, but with the changing of Mrs. Joe's attitude and temper, her position reverts to Pip's sister.