Illus. in full color. Cassie, who flew above New York in Tar Beach, soars into the sky once more. This time, she and her brother Be Be meet a train full of people, and Be Be joins them. But the train departs before Cassie can climb aboard. With Harriet Tubman as her guide, Cassie retraces the steps escaping slaves took on the real Underground Railroad and is finally reunited with her brother at the story's end. "Cassie learns her people's history well; so will readers of this impressive picture book. Ringgold's dynamic paintings combine historical fact with strongly realized emotions."--(starred) Booklist. "Groundbreaking!"--(starred) School Library Journal.