This book has highs and lows--stars are the average. 
 There are two plots, one during World War I and the other more current. Mostly they are signaled well and the back and forth fairly well placed. AFter the second is introduced, readers quickly learn the connection, though the main conflict takes a dozen or so more pages to be revealed. From there on, it is hard to put the book down. 
 Sophie, the WWI heroine, is presented at first as feisty and fast thinking. One thinks of The Zookeeper's Wife and her various close calls averted by on-the-spot thinking. Disappointingly, Sophie makes some decisions that don't seem congruent with that first picture, but the plot depends on them.