This letter includes the full text of another letter Celie has received—from Nettie. The letter from Nettie says that she, Nettie, is safe and happy, and so are Olivia and Adam. The letter implies that Nettie has been writing to Celie all along, but that, somehow, the letters have not reached Celie, since Celie has not responded. It is not clear when exactly this letter was sent to Celie, but it appears Nettie wrote it shortly after leaving Mr. ____'s house, and moving in with Samuel and Corrine.
One of the novel's shocking discoveries. It turns out that Nettie has, in fact, followed up on her promise to write to Celie. It is not clear whether Nettie is still alive, as this letter was sent years ago, but it does appear that Mr. ____ has been hiding evidence of Nettie from Celie. Celie cannot believe that Mr. ____ would be capable of such cruelty.
Shug reports to Celie that she has seen Mr. ____ at the mailbox, taking letters with "funny stamps" and putting them away, not showing them to Celie. Shug asks Celie about Nettie—if she was smart and what she looked like—because Shug knows that Nettie is the only woman, other than Shug, that Celie has ever loved. Shug and Celie begin to suspect that Mr. ____ has been hiding Nettie's letters to Celie. Celie, for her part, had no idea that Nettie was even alive and writing to her.
Shug has spotted Mr. ____'s perfidy, but until now, she did not realize what exactly Mr. ____ was doing. Shug recognizes the importance of Nettie's relationship with Celie. In some sense, Shug and Nettie are the most immediate of Celie's family—the only two people in the world Celie trusts to share her darkest secrets. Shug's questions about Nettie suggest a little bit of jealousy; that she perhaps likes being the sole living person whom Celie loves.