In 1864 twelve-year-old former slave Charlotte is lucky enough to live on a plantation near Richmond, Virginia, owned by a Miss Van Lew, who hates slavery, and when Charlotte overhears a conversation she realizes that her mistress is gathering information and passing it on to the Union army; Charlotte is eager to help, (especially since her own cousin, Mary, is involved) but her enthusiasm may endanger them all--or help free 400 Union soldiers who are being moved from Richmond further south.