Hello,
Answer: The book Lilies of the field the general theme would be of the many people the power of praying and having much faith in one and another.
My work: The book was about five German speaking nuns who tried to escape from the threatening communist from Eastern Europe and throughout the story there is constant prayer for help and for safety. It some parts it might not be told in physical words, but it gives you thoughts of the readers to keep faith and for those nuns to keep going!
I Hope it helps!