Marriage, as the knot in question, is exemplified by the union of Marian Lind, a lady of the upper class, to Edward Conolly, always a workman but now a magnate, thanks to his invention of an electric motor that makes steam engines obsolete. The marriage soon deteriorates, primarily because Marian fails to rise above the preconceptions and limitations of her social class and is, therefore, unable to share her husband's interests. Eventually she runs away with a man who is her social peer, but he proves himself a scoundrel and abandons her in desperate circumstances. Her husband rescues her and offers to take her back, but she pridefully refuses, convinced she is unworthy and certain that she faces life as a pariah to her family and friends. The preface, written when Shaw was 49, expresses gratitude to his parents for their support during the lean years while he learned to write and includes details of his early life in London. --Wikipedia.com.