Betty is living in England with an aunt's family after the tragic death of her mother and brother, and is approached to be a spy because of her fluency in French and German. Soon, she is Adele, and parachuting into Nazi-occupied France to work with the Resistance. With her is Denise, who operates the radio they use to communicate with headquarters. Since the Nazis don't suspect girls to be much trouble, the two are able to add a lot of information to the Resistance-- Adele is taken on a tour of a munitions factory by a German guard, the two go to a party hosted by people sympathetic to the Nazis, and they always manage to escape the round ups and check points. When it seems that there is a double agent in their midst, Adele must work to find out who it is before even more people are killed.
Strengths: Wow. This is the best thing I have read for a while. World War II adventure and espionage... from a girl's point of view. I can almost see the appeal of war books for boys after reading this. I've never gotten it before, because I wouldn't want to shoot at people in combat, but I could envision myself as a spy. Adele rides about the country side on a bike... I could SO do that. The details of every day privations and danger are exquisite, and there are two nice romances. One is with Pierre, the tragic French Resistance fighter, and one is with Robbie, an underaged pilot who is rescued by Adele when he is shot down.
Weaknesses: I would have liked a few more historical notes at the back, and perhaps a map.