Lady to Kill — Lester Dent

To get to the bottom of a business deal gone bad, Chance Molloy seeks answers from a young woman on a train -- but gets more than he expected

Julie Edwards, a small-town physician's assistant, is headed to New York to visit her old friend Martha and make a new life for herself. On the train, she meets Chance Molloy, an intrepid, self-made airline owner who also knows Martha -- or thinks he does. When Molloy shows Julie a picture of their mutual friend, she claims he's got the wrong girl. As Julie walks back to her car, an assassin knocks her unconscious. She's saved in the nick of time from being thrown off the train.

While the train hurtles forward, Molloy must unlock an elaborate corporate conspiracy surrounding the imposter Martha, while safeguarding Julie and staying two steps ahead of the killers traveling with them.