K. - Mary Roberts Rinehart

"K" is the initial of the mysterious lodger without a first name who rents a room from Sidney to escape his past. Sidney herself refuses the proposals of Joe in order to become a nurse and do useful work in the outside world. She is determined to work hard and not spend any time at all with the handsome young surgeon who runs the ward. She has no time in her life for romance, or for exploring the mystery of K's background. Or does she? (Summary by Beth Thomas)