Nancy and Plum (whose real name is Pamela) are sisters who were orphaned when their parents died in a train wreck six years ago. Without properly investigating it, their guardian, Uncle John, sent them to Mrs. Monday's Boarding Home in Heavenly Valley. Ever since then, he has had very little to do with them. Mrs. Monday seemed kind, but she's really menacing and cruel to all her borders except her horrid niece, Marybelle. Despite their miserable life at Mrs. Monday's, Nancy and Plum are cheerful children. One of their favorite things to do is sneak out by way of the tree next to their window and help Old Tom, Mrs. Monday's kindly brother, who takes care of the cows and chickens in back of the boarding home. One day while the girls are attending a school picnic, Uncle John comes to visit them. but leaves before the girls return. When the girls come home they find out about his visit and that Marybelle and Mrs. Monday purposely detained the girls' return home so they wouldn't be able to visit with him. That night the girls decide to run away, so they pack up all their treasures in some handkerchiefs and, with the help of Old Tom, climb over the spiked fence. Will they succeed in running away? Who will be their new family if they do?