Secrets: The Time Machine Girls

Don’t go in the attic. Out of the 100 rules their grandparents gave them to follow, that one was the most important. So, of course, it was also the first one eight-year-old Hazel’s little sister, Bess, decides to break. But she never expected Bess would accidentally uncover a dark family secret that involves a hidden time machine and their mysterious, and grumpy, grandpa.