Sixteen-year-old Zinnia Winterschild has known all her life she would someday fail the Test that would allow her to become a citizen of the Nation. The one thing she didn't know was what would happen afterwards. The only other person that failed the Test from her community disappeared, and seemingly disappeared from the memories of everyone else as well. She has always been told that this "great Nation" cultivates geniuses after humans destroyed the earth during World War III; that because she was stupid, she would never become a citizen of the Nation. However, when Zinnia inevitably fails and is thrown outside of the Wall with a group of kids from different communities who also don't pass, she realizes everything she has learned about the Nation was wrong. The last message from her mother, the dreamer and the rebel, was to trust no one. When Zinnia finally comes upon the crossroad of shadows, will she have the strength to heed her mother's last warning?