Grace Livingston Hill 
Time of the Singing of Birds [EPUB ebook] 

Pretty, petite Margaret Roselle is overjoyed when Barney Vance returns safely from war. Then Barney tells her that their friend "Stormy" is missing behind enemy lines — and that he has decided to return to enemy territory to find him! Faced with the reality of the danger in Barney's chosen mission, Margaret finds strength and peace in her undying faith.
No matter what happens, she is sure God will take care of both her and the man she loves…