Alongside Tokyo's Sumida River is a ragpickers' settlement known as Ant Village. One night, a young Catholic girl, Satoko Kitahara, who has been baptized under the name of Maria, comes to offer her services. However, Ant Village is not just an ordinary vagrants' community but a fine autonomous organization, and as the municipal authorities have long been demanding that the people of Ant Village leave the site, Satoko is utilized to publicize the Village and win public sympathy. While being utilized in this manner, Satoko is nevertheless glad to be able to help the people of Ant Village, especially the children, and when the summer vacation comes she decides to take the children on an excursion to Hakone. To raise funds for this purpose she becomes a rag-picker herself.
