Great time travel and the best mystery novel I think I ever read. If you mess up history can you go back and fix it? What if another conundrum shows up on every other page? This book is full of twists and turns and where part of the answer occurred to me late in the book you never know until the end. Connie Willis is the master of chaos. I was not even sure what the mystery was as it too seems to change as the book goes on, is it the missing bishop’s bird stump, did saving a cat change history, did returning it to the past make it worse? How can a cat in 1888 allow Hitler to conquer England and is it wise to send someone back to fix it that has time lag so bad he doesn’t know where he at?