What is the most important detail in Chapter 6 of ''When Zachary Beaver Came to Town''?

In my opinion, the most important detail in the sixth chapter is Wayne's letter. Wayne's tone, his writing, and his obvious sadness should have sparked a response in his brother..... should have made them aware of the horrors he is experiencing. His brother, however, retain his innocence. Toby, however, feels that something is amiss and encourages Cal to write back.