An enjoyable story about a girl who becomes involved with the U. S. Secret Service during WWI. The plot proceeds at a brisk pace and has some good action and romantic elements. The twist at the end was rather predictable, but that did not detract from my enjoyment.
One quibble: Despite the main character being a twentysomething girl, she is portrayed as though she has the mind of a 10-year-old girl. Perhaps that is how many girls acted back then, but I found her naivete and reactions to be a bit over-the-top at times.
An interesting mystery that became more and more complex as the story progressed, with some good twists along the way. I liked the psychological element whereby certain characters would give or withhold key information at various points in an effort to fulfill their personal agendas. Although I enjoyed it, I was ultimately disappointed by the solution, which I thought was somewhat weak.
A good action-adventure story that held my interest, even though some events were rather far-fetched. I thought the ending was a bit anti-climactic.
Despite having enjoyed many of Agatha Christie's other stories involving Poirot, I did not like this one. The plot was rather boring and the ending was dissatisfying -- key clues were withheld from the reader until after the solution to the mystery had been presented. Moreover, Poirot seemed to magically know who was lying and about what, even though there was little evidence that strongly pointed to any particular statement being a lie.