I Love This Book!
This is a great book set in World War II. It has espionage, parachute jumping, betrayal, danger, disguises, the works.
Jean hears that her cousin Giselle, an Underground agent in France, has been captured, tortured, and rescued(but still not safe). She decides that she must go and bring her back to England. Following that come weeks of training, during which she learns to parachute jump. When she is dropped in France, she goes to a mental asylum, where Giselle is being kept. After Giselle is well enough, they go to get her two girls, Angelique and Jacquie, from where they are being kept safe. Then comes a daring escape, and I'm not going to tell you any more except that they get to England and are still in danger, because you have to read this book. It's terrific.