It was much longer than her previous three novels, and its tone, pace, and purpose were significantly different. It depicts revolutions without veering into quaintness or romanticism, and is instead permeated with a sense of historical reality. A gentlewoman whose children die of smallpox experiences a growing intimacy with her estranged husband's mistress, and the two women become involved in the two revolutions taking place in Paris in February and June 1848. The women eventually espouse the Communist cause.

The Public Health Act (Scotland) provided for the setting up of isolation hospitals: local smallpox was eradicated in seven years from this Act, after 34 years of compulsory vaccination had failed.

The act also made arm-to-arm vaccination illegal. It had constituted a real danger to pauper children, who received the virus from other pauper children who occasionally communicated other diseases together with smallpox immunity.

MB 's mother had married her father on the rebound, and they were incompatible by temperament, although both equally opinionated, forthright, and tactless. Bertie found early in the marriage that Charles had gambled away the joint savings they were setting aside for a house. They had constant acrimonious quarrels about money until he allowed her to take control of his salary, allotting him only a little pocket money. After this they found other things to quarrel about. Charles had an affair when Muriel was still a baby, and after this the couple became sexually estranged. On one occasion Charles Baker was goaded to hit Bertie, then slammed out of the house, leaving her to sing lugubrious hymns all day. One of the rare things they agreed on was going through the rigmarole of conscientious objection so that their children did not have to be vaccinated against smallpox.

EJ published another novel, Brightness, with a leading character modelled on an uncle she had never known, Romilly Ingram , who had gone to India as a missionary and died young of smallpox in 1898.

ML 's childbirth experiences were not propitious. Her daughter was delivered by forceps (at the Elizabeth Garrett Anderson Maternity Hospital in London, UK) after a 36-hour labour, and the delivery cracked the baby's collar-bone—a not unusual occurrence, ML was assured. The bone healed within ten days. Jocelyn lived through a greater danger at two months, when her smallpox and yellow fever injections, for Africa, were administered too close together and in the wrong order. The baby went into convulsions, while the doctor concerned (who was angry with Laurence for insisting on continuing to breast-feed while her daughter was severely ill in hospital) ascribed the convulsions to either a congenital tendency or else meningitis. Two years later another doctor admitted that the first had been at fault. When Laurence got pregnant in Ghana a pregnancy test falsely registered negative, netting her a diagnosis of neurotic, and after that she had two false labours before managing a swift natural childbirth, assisted by a reassuring black midwife. A white nursing sister spoiled the experience slightly by forcing her to eat while in labour although she said she would throw up, which she duly did.

The World Health Organization 's Resolution 33.3 recorded the global eradication of smallpox (announced the previous December).

Frederic and Caroline, or the Fitzmorris Family, 1800, another novel in two volumes, tells the story of the Fitzmorris family (with two generations of Frederics and Carolines). Its attribution gives it to the author of Rebecca, Judith, and Miriam, and like Emily of Lucerne it is dedicated to the Princess of Wales. In an interesting Preface the author apologizes for using quotations without attribution, but she implies that books are inaccessible to her: she says she is fixed in a spot where literary amusement must be purchased, and when, she enquires, did the purse of an Authoress overflow with cash? It would be a mistake to read too much into this about Foster's life, but it is interesting that in a year when she published four books, she constructs a narrator who complains of the low proceeds that writing brings. The novel also has a scene set in the Minerva Circulating Library . The novel opens in 1798, with the description of a mysterious and melancholy man known as Sandford who has purchased an estate in Cornwall. He befriends the local rector, Mr Godfrey, and his two children, Emma and Frederic. The Godfreys turn out to be the family of his sister, who had been disowned for marrying beneath her and who has long since died. Godfrey and Sandford are delighted to find each other, and Sandford undertakes to offer support for Godfrey's two children. Sandford's melancholy is revealed to be the result of a disastrous marriage to a wife who eloped with another man. She took their baby but left behind two older daughters, who then died of smallpox. His wife, long since repentant, has raised their daughter Caroline to be virtuous, and Frederic Godfrey has fallen in love with her, without of course knowing their connection. Caroline's mother insists that Caroline renounce Frederic until her death, and their separation is further complicated by the unscrupluous behavior of Caroline's other suitor, Mr Mortimer, who lies and bribes servants to effect the estrangement of the lovers.