The promised child follows Mendel Pulichever, a childless rabbi in the fictitious Polish town of Pulichev. After hoping and praying for many years, he is finally blessed with a baby, whom he names Shloime (nicknamed Shloimele by his mother). Shloime subsequently turns into a brilliant little boy and becomes the toast of the town and the heir apparent to Mendel's job as rabbi of the city. Unfortunately, the boy is kidnapped by a local priest, Zbignew Mzlateslavsky, who is a bitter man, jealous of Mendel's happiness. All of Mendel's efforts to search for the boy are fruitless as he is hidden in an orphanage and is brought up as a Catholic. Eventually, Shloime, who grows up under the name Gregor Tal, attains the rank of bishop within the Catholic church and has little memory of his early childhood.