Does it have to be PROBABLE, too?

You could always put in a simple little note before getting involved with the "possible" scenario.

Something like (an example only): "While it can only be speculation, it's possible that [something that could occur]; while this may not be probably given the fact of the case, it is at least plausible and worth considering . . . "

I don't think you have to (or should be) limited by sticking with the "probable". If something could have happened within the established timeline, evidence, etc, I'd call that fair game.

Heck, I'm planning on making a very prominent character of the next WIP a homosexual. There's nothing attesting to this in the sources, but then there wouldn't be, given the attitudes of the 6th century church. But making this individual a homosexual would explain a lot of bizarre interpersonal behavior.

Was it probable that this individual was gay? I don't know, but it is certainly within the realm of possibility...

Think in terms of other genres, specifically sci-fi and mainstream that borders on sci-fi. Was Jurassic Park possible, probable, or not even possible? Think about the fiction books/movies about volcanoes erupting somewhere - possible, probably; probable, ? Or even the James Patterson woman killing books.

In a case like this, I don't think you should limit your thought process to just historical fiction. But, if you're concerned because it is historical fiction and based on real events, include an author's note at the beginning saying something like - No one knows exactly what happened in the Diamond Necklace Affair, the historic record is incomplete. But, after reading and reviewing all the documentation available, I chose to present the story as it appears in this book because - it could have happened this way.

Hope that helps. Puma

Posiible and plausible, yes. But probable? No! Probably nothing interesting will happen today. If you put a random man and woman in a room together, there will probably be no romance or intrigue. There is probably no one with a credible plot to topple the House of Windsor right now. That stranger who just cut me off in traffic is probably not my long-lost nemesis and twin cousin.

Etc, etc...