I agree about not calling names. It took two to tango.

I wonder, however, what about his affair with this woman, are you hoping to gain insight, into?

If it's to wonder what she had, that you didn't, I can see how that wouldn't be conducive to moving your marriage forward.

If it's to find out, why he would stray, and how to protect yourself from that ever happening, again, then getting down to what brought him to that point, would be a good start.

It's all about the motives involved, when asking the question. You are angry with her, him and I'd presume yourself.

It's a grieving process to reach the point of forgiveness.

I'd imagine, being a position of him returning, because the affair ended, I'd personally feel a lot insecure about why he came crawling back to you, so to speak.