This book was beautifully written with amazing word choice and a unique plot. Addie and Zachary are siblings, but they don't know it. When they travel back in time in a museum, they start to communicate with each other through a strange mailbox, not knowing that they are writing to their siblings. They go through farm life with families from older times and learn just how hard it was to survive back then. They make friendships and live through tragedy, but sooner or later they have to go back to the real world. But the question is: How?