Rebelling against her monotonous life, young Claudia Kincaid (Jean Marie Barnwell) runs away with her brother, Jaime (Jesse Lee), to the Metropolitan Museum of Art, where they embark on a grand adventure. While there, they become captivated by a new exhibit: a marble angel. To learn the name of sculpture's creator, they must find the reclusive Mrs. Basil E. Frankweiler (Lauren Bacall). Without her help, the siblings may never find their way home.