Grace Livingston Hill 
The White Flower 

Lovely, flame-haired Rachel Rainsford thinks she is on her way to take a job in Chicago. Then she discovers that her new employer is a criminal who actually plans to sell her as a “companion” to a wealthy and unscrupulous businessman. Even worse, through a series of lies, the two men have made sure no one on board the train will help Rachel escape. Friendless and penniless, Rachel seems doomed.
Then, suddenly, a handsome young man steps in. Together, he and Rachel make a daring escape from the train. But the criminals refuse to give up, and Rachel and her new-found champion soon become the prey in a desperate chase that will test their faith and courage—and lead them into love.