In 1857 twelve-year-old Libby joins her father aboard the Christina and proves that she can be trusted to assist in the escape of a fugitive slave.

On the Cristina's trip up the Mississippi, Libby Norstad and her friends meet a talented violinist who seems to have secret. Libby is set on discovering what it is, but when they arrive in St. Paul, his violin is stolen. Libby, Caleb, and Jordan lead the search, but find nothing. Then the fugitive slave Jordan meets his biggest enemy, and takes on a new role in the Underground Railroad.

In 1857, while working for the Underground Railroad on a Mississippi River steamboat, thirteen-year-old Libby hunts for the swindler who has robbed her father and tries to reunite the fugitive slave Jordan with his missing father.

Kate, Anders, and Erik investigate baffling clues that lead them to tunnels in the woodpile, stolen food, and a hidden ladder.

When her mother marries Mr. Nordstrom, Kate moves to a farm in northwest Wisconsin, solves a mystery, and learns to adjust to her new stepfamily.

After Kate buys Windsong and Breeza, two horses with a mysterious past, someone sets the Nordstrom barn on fire and Windsong disappears.

In 1907 in Wisconsin, Kate and her friends discover a timber swindler while visiting their Indian friend Running Deer and suspect that Kate's uncle, newly arrived from Sweden, may be involved.