When sisters Sadie and Zuzu move to Salt Lake City, they discover an old journal in a secret room in their new house. Along with their neighbor, Bella, the girls take turns reading the story of a girl named Helen who lived during the flu epidemic of 1918. They soon become wrapped up in Helen's tale, which ends with a tragedy that has a scary parallel to Sadie and Zuzu's lives. Did Helen survive the flu? Is she still alive somewhere? Or could her ghost be watching them?