It was the slap heard round the world or amongOutlanderfan groups, at least!
(In the book, Brianna only moves to hit Jamie but doesnt connect.
This blog post fromOutlander Homepagedoes a good job of comparing screen versus book scenes.)

Credit: Aimee Spinks/Starz
SOPHIE SKELTON:We were trying to show that Brianna is Jamies daughter.
Not that he goes around hitting people, but Claire slapped Jamie before.
Its not totally Jamies fault, and in those days that would be the attitude, unfortunately.
With the Brianna story line, I delved into research about victims of rape and how their responses differ.
In that moment, I think anyones response is going to be different.
Youre in defense mode.
MATTHEW B. ROBERTS:The audience is from the 21st century.
How would I react?
We sometimes have to reel that back and ask, How would Brianna react?
Obviously she goes on to punish her cousin Ian, too.
She goes on a bit of a tirade.
Shed been verbally slapped, so she just kind ofreacts.
Because we get it, weve read the books.
The people who know and love the books fill in the gaps.
Then you get someone whos never read the books who reads it and goes, What?
I dont get how Jamie did this or Claire did that.
Youve got to make that person understand, too.
Ill have lots more from the set in the coming months, including fresh scoop about the new season.
Keep checking back to EW.com for all of yourOutlanderneeds!