Favor (short story)

I’m about to fuck this girl as a favor to a friend.  She’s his wife.  He wanted to know if she’d been cheating on him & his way to find out was by seeing if she’d sleep with me.  I wish he’d hired a private detective instead.  Because I feel like all this proves is that I’m an asshole.  I’m about to fuck my best friend’s wife.  What kind of person does that?  Maybe I should tell her why I’m with her.  Give her a chance to repent, to save her marriage.  No matter what I’ll end up needing to get a new best friend because I won’t be able to deal with the guilt of having let things get this far.  What the fuck am I thinking?  I’m over analyzing things.  I should just fuck this girl & go the fuck home.