As he walked back to his seat, David pulled a small hand mirror out of his pocket. Once he was sitting again, he pulled out a book and laid the mirror against one of the pages, allowing him to watch the three Russians as the flight went on. There didn’t seem to be a problem. David doubted they had even noticed her. If they had, they probably didn’t recognize her.

It was probably just a coincidence. Three men getting on a plane, flying back to Philadelphia. Three men in the ...