Nettie's next letter shows Nettie's increased anxiety that Albert is following through on his promise—that he is not, in fact, delivering Nettie's letters to Celie, but rather hiding them somewhere, and that this is preventing Celie from responding to Nettie. Nettie says that Samuel will not let Nettie visit Celie, since he believes it is wrong to "come between a man and his wife." Nettie begs Celie to write back, and includes stamps in her letter to her sister.
The Reverend, who is a man of principle, nevertheless acts on a Christian principle, here, that some might find misguided. Sure, marriage is a sacred contract, but Nettie has good evidence that Mr. ____ has been abusing Celie. This, however, is not sufficient cause for Samuel to get involved in the affairs of another couple.