Philip K. Dick:
His ex-wife. He hadn't thought of her in years. Well, months. Weeks, certainly. She'd been a brilliant computer scientist, the valedictorian of her Positronic Complexity Engineering class at the UNATS Robotics school at the University of Toronto. Dumping her husband and her daughter was bad enough, but the worst of it was that she dumped her country and its way of life. Now she was ensconced in her own research lab in Beijing, making the kinds of runaway Positronics that made the loathsome robots of UNATS look categorically beneficent.
He itched to wiretap her, to read her email or listen in on her phone conversations. He could have done that when they were still together, but he never had. If he had, he would have found out what she was planning. He could have talked her out of it.