Plausible reaction. Solid characterization.

It might have worked well to interrupt Robert's thoughts with external events, i.e. a description of his body language while he ponders his predicament. The whole set up of Robert sitting at the stream would have deserved a few more words, to make it more visual. Images are a good way of underlining or contrasting what is thought (or said)...

Will there be another encounter?

Will the father find out?

Will the Earl feel cheated out of his eldest son? What about Guisburne's stepfather?

And what would it take to make Guisburne spare his brother?

Somehow this part of the show's canon opens a lot of interesting possibilities.

I like this. It realistically delves into the conflict Robin has over the whole situation. I would love to read a story revolving around what you put in the first paragraph, the rescue, the confrontation, the reconciliation, Since you've gone past that in this story, you could do a flashback. Just a thought. Will there be more in this series?