Affair partner's spouse contacted me. What do I do??

Do nothing. Don't respond.

You should have told your wife way before this , anyway.

Close down the FB account. Be a better husband.
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Thank you for your advice.

The affair is over, when my wife asked a year ago I couldn't handle lying anymore. I told her. It's been a hard year. I am trying so hard to be a better husband, trust me. I know I can't make up for what I did but I also know we can make our relationship better than it was even before my failure.

Sorry I left out those important parts of the story. And I meant tell her about this message, not that she doesn't know about the affair. I'm kinda freaking out right now, where normally I'm around a zero on the 0-10 anxiety scale.

What good would come of it if you were to tell her that there has been a contact related to this regretable offense?

Why stir the pot?

No need to tell your wife. You two are working to restore things and bringing this up to her can only serve to reopen an old wound.

As far as the message itself, ignore it. It would not have been good to respond even if you had seen it the day it was sent to you.