Judgment by Joseph Finder

Every time you think one little action won't have any consequences, life tends to show you how very wrong you are. Judge Juliana Brody is in Chicago for a legal conference and even though she's normally a rule-follower, she ends up having a one-night stand. Though she feels guilty about betraying her husband, she thinks life will go on. Then she sees the guy from Chicago in her Boston courtroom as the newest member of the legal team on one of her high-profile cases. And she realizes that can't be a coincidence. Before she can say, "I shouldn't have had that second Chardonnay," Juliana realizes her marriage, her career, her reputation, and maybe even her life are at risk. And she decides to fight back. (I had to admire her ingenuity in the way she fought back, since she was basically an average Jo, and not someone with special spy training.)

I first discovered this author when I read his equally engrossing novel Switch.