Lyman starts off this chapter with a mysterious disclaimer: though he knows what happened next, he's less sure about the how and why of the situation.
This problem is caused by the fact that Susan only writes one letter between July and September 1890. Strangely, this letter is merely "one sentence" and is sent from Chicago (8.7.2).
There are a few newspaper articles that fill in the gaps of the story. The first is a small article from July 22 talking about how Susan and Betsy are heading east to bring Ollie back to school.
We get more vague talk from Lyman. He keeps dropping hints at something big, like when he casually states that Susan is "grieving" at the time (8.7.9).
Ollie wouldn't come back home for another 10 years. Wow. Even more strangely, Susan didn't let him spend any time with family in Milton and instead hauled him straight off to school when they arrived.
But, why? All we get for answers are more vague statements: Lyman believes that Ollie (his dad) blamed Susan for "the catastrophes" that had hit the family over the past several days (8.7.12).
Susan isn't planning on going back west, either: she tells Augusta in a letter that she will be moving to New York to focus on her career as a writer and artist.
But, Susan doesn't. In fact, that single letter we mentioned previously was actually her apology to Augusta for skipping out on her promise.
Finally, Lyman reveals the truth that he's been avoiding all chapter—young Agnes drowned in the Susan Canal on July 7. That's awful.
The next revelation is even bigger—Frank Sargent shot himself on July 10, two days after Agnes' funeral. That's pretty awful, too. But, what does it all mean?
Lyman lays it out for us: he suspects that Susan was unable to keep herself from Frank after their little Independence Day tryst, leading the couple to meet secretly along the canal.
But, Susan needed some cover: some "camouflage" (8.7.47). That's where Agnes comes in. Lyman suspects that Susan brought Agnes along as an alibi but lost track of the girl during her time with Frank.
The newspaper article states that Susan started screaming when Agnes went missing and was met by Oliver and Ollie. Tellingly, the article also mentions that Frank assisted in the rescue efforts.
Wow. Although it seems far-fetched, Lyman's logic makes a lot of sense.
Lyman shifts gears to tell us a story about "the business of the rose garden" (8.7.52). Doesn't seem relevant, but we'll allow it.
About 40 years ago, Lyman was helping his granddad in the rose garden when his Aunt Betsy came by to say hello. She stopped to admire the flowers but then asked her father if he remembered ripping up all of the rosebushes from their house in the Mesa decades earlier.
Lyman pictures the scene: Susan's looking out the window as Oliver pulls up every single one of the roses he had spent so much effort planting.
In his heart, Lyman feels like his grandfather was too uncompromising. He suspects that ol' granddad felt the same way but was too ashamed to admit it.