I think they make the changes to “spicy” things up a little bit because “The Black Moon” would be hard to translate into the screen the way it was written IMO. Not much if anything happens in this book until Ross goes with his rescue mission to France, and tv series format demands more action/adventure or at least some tension to keep people engaged.
That some of those changes are questionable is a different matter. I agree about Elisabeth though, with one exception – the book makes it quite clear IMO that she didn’t love Valentine as much as she loved her first born.
I like what they are doing with Morwenna/Drake/Geoffrey Charles here though. In book Morwenna has zero personality but the the actress’ charm make her quite captivating on screen.

By the way, Demelza had no right to allow her brothers to use the barn on the Nampara estate in the first place. She was never thrilled with or supportive of Sam’s attempt to establish a Methodist church in the area. Neither was Ross. Also . . . Dwight and Caroline got married in the 1976 novel, “The Four Swans” – after his return from France. And they had a big wedding ceremony and reception, not a private wedding.

It’s one hting to make a few changes here and there when adapting a novel. It’s another to completely rewrite it with unnecessary changes, especially a first-rate novel like “The Black Moon”, which was regarded as one of Winston Graham’s better additions to the saga.

This episode was a travesty. Season 3 is proving to be a travesty.