SPOILER ALERT: Dinna read unless you have finished An Echo in the Bone.
So I've been doing some serious pondering and surmising about "Book 8". Allow me to share.
I was brushing my teeth and thinking about how much I miss the Outlander crew. I then said to myself, "Self", I said, "what on earth is Book 8 going to be about? Is it going to grab me from Page 1?" I then thought "Oh it's going to start off with Jamie finding out about Claire sleeping with Lord John... so of course it's going to grab me." I then did the usual pondering about Claire sleeping with Lord John and what Jamie's reaction is going to be... yada yada yada... we've all been there a thousand times in our heads.
And that's when it happened. "Self", I said, "what is Willy's role going to be in Book 8?" And all at once, I knew. Jamie and Willy are going to rekindle the relationship they forged all those years ago at Helwater and truly become father and son. Ask me why I think this. Go ahead. I'll wait.
HERE'S WHY: THAT'S why Claire HAD to sleep with Lord John. Diana probably thought to herself, "Well, I'd like to form that father and son bond between Jamie and William - but how in the world can I do that with William's relationship with his "father", Lord John... and with the respect Jamie has for his best male friend in the world?" And that's when she probably said to herself "Lord John has got to do something so awful, so hideous that Jamie won't feel the least bit bad getting close to Willy as his true father"...
And then she probably said "But what? What on earth could Lord John possibly do that would make Jamie THAT mad?"
And the rest, my friends... is (future) history.