After her mother's death, Carol Rose finds her mother's treasure box in the attic. This box contains her mother's childhood treasures: a white feather, a whistle, a paintbrush, a journal, a ring, a compass, a bottle of oil, a little purse, and a broken star. There is also an envelope. She opens it and a note falls out. After she has picked it up, she reads quietly, "Whoever is the first person to open this envelope will be the one to complete the mission." Then suddenly, she hears the voice of an angel. The angel tells her that she is chosen to restore the Star of Hope in Greenfield so that children will be reminded of the hope and may believe that they will reunite with their parents in Heaven. As well, she is told her brothers and sister will aid her in the mission. Then Carol Rose, Olive, Timothy, and Sam find a mirror in the attic. They walk into the mirror and enter another world through a time tunnel. And then their adventure begins.
On their journey, however, Sam is captured by Mrs. Diplock, an important spy of the wicked Queen Juliana, and he is imprisoned by the queen in her castle. In the children's attempt to save Sam, Carol Rose is killed by the queen.
Can Olive, Timothy, and Sam escape? Can the mission be completed?