 After Eva Snyder becomes an orphan, she comes to live with the elderly Mississippi riverboat Captain King Snyder and his old maid sister Nell. While the Captain is piloting his boat, Nell finds it difficult to govern Eva, who constantly talks to imaginary friends whom Eva believes are real, including Mingo and her father Mr. Peppercorn. When the Captain returns, he presents Eva with a gift--a black doll named Numa. Nell hears Eva chatting and playing with Numa, but suspects that it is a child from the neighborhood. Eva warns that if Nell takes Numa away, Eva will trade places with Numa and go to the idyllic place "where the woodbine twineth." When Nell puts Numa on top of the player piano, Eva steals Numa away, and the piano mysteriously plays by itself. Nell finds Eva in the backyard with a black girl playmate, and Nell chases the girl away, warning her to never return. Then Eva disappears. When Nell finds a doll in Numa s box that looks exactly like Eva, she tearfully realizes what has happened.