The book is broken up into four parts. The first section, "Mrs Baines" details the adolescence of both Sophia and Constance, and their life in their father's shop and house (a combined property). The father is ill and bedridden, and the main adult in their life is Mrs Baines, their mother.
By the end of the first book, Sophia (whose name reflects her sophistication, as opposed to the constant Constance) has eloped with a travelling salesman. Constance meanwhile marries Mr Povey, who works in the shop.
The second part, "Constance", details the life of Constance from that point forward up until the time she is reunited with her sister in old age. Her life, although outwardly prosaic, is nevertheless filled with personal incident, including the death of her husband, Mr Povey, and her concerns about the character and behaviour of her son.