In 1851, thirteen-year-old Cecilia has her eyes opened to the horrors of slavery when she accompanies her ornithologist uncle on an expedition in search of the rare "Scarlet Ibis," and watches as he shows slaves the way to the Underground Railroad.

This time the mysterious box that Ranger the Golden retriever found transports him to a Maryland plantation before the Civil War, where he must help a young house slave named Sarah and her younger brother Jesse find their way to the underground railroad and North to freedom, before Jesse is sold to a plantation further South.