The story opens in the “barton”, or milking yard, of a large dairy farm in the water meadows between Dorchester and Wareham in south Dorset, at some time around the year 1820. The milkmaids are hard at work and talking among themselves about the young wife that Farmer Lodge is about to bring home. One topic of conversation is how Rhoda Brook, one of their number who is milking on the other side of the barton, must feel about it.
When milking is over and everyone is going home, Rhoda is joined by her son, who is not named but is described as being aged “twelve or thereabout”. It soon becomes clear that Farmer Lodge is the boy’s father, a fact of which the boy is well aware. When they reach their cottage Rhoda asks her son to act as a spy to find out what the new wife looks like, as she is clearly curious about who the farmer has decided to marry, having refused to do the right thing by her more than a decade previously.
The boy makes sure that, when he goes to the market the following day, he is at the right place on the roadside to see the farmer and his wife pass by in their horse-drawn gig, and for them to see him. Farmer Lodge clearly knows exactly who he is but does not let on.
Rhoda sends the boy to church on Sunday, expressly to gather more details about Gertrude. Rhoda asks him many questions when he gets home, so she soon has a very good idea about the woman who, as she sees it, has supplanted her. Rhoda’s obsession becomes so intense that she can think of little else, although she takes care never to see Mrs Lodge for herself.
One night, a few weeks later, Rhoda has a vivid dream in which Gertrude comes to her at night in the form of an incubus (a demon that is typically male but in this case is not) that sits on her chest and mocks her by flashing the hand that bears a wedding ring in her face. In her vision, Rhoda is so incensed that she grabs “Gertrude’s” left arm and throws her down. On waking, she is convinced that Gertrude must have been there in person, given the strength of the vision.
The experience makes Rhoda ill, and her condition is not improved the next day when her son says that Gertrude has spoken to him and intends to visit their home to bring him a present of a pair of boots, as she has seen that his are worn out. When this visit takes place Rhoda is taken aback by the kindness that Gertrude shows and reproaches herself for her previous attitude.
Gertrude makes further visits and, before long, the two women start to become friends, despite the huge difference in social standing between them. However, now that Gertrude feels able to share confidences with Rhoda, she tells her that her left arm has been giving her a lot of trouble lately. When Rhoda sees the arm she is horrified to see that it bears the imprint of four finger-marks, as though it had been roughly grasped by somebody. Of course, Rhoda immediately sees their significance, especially when Gertrude says that she first noticed the marks on the morning after Rhoda’s vision, but she does not dare to tell Gertrude about it.
As the arm gets worse, Gertrude mentions that she has tried everything she can think of to cure it but to no avail. However, she has heard about “Conjuror Trendle”, who lives in an isolated cottage in the heart of Egdon Heath, who might be able to help due to his supposed possession of “powers that other folks have not”. Gertrude wants Rhoda to go with her to Conjuror Trendle’s cottage and, despite Rhoda fear that this might lead to Gertrude learning the truth about how she got the injury, agrees to do so out of friendship.
When the visit is made, Conjuror Trendle says that the injury is “the work of an enemy” and that he has a trick (involving the victim looking into a glass of water to which the white of an egg has been added) that will reveal who that enemy is. Gertrude goes through this process but will not say anything to Rhoda afterwards about what she has learned. However, after this incident Rhoda becomes even more withdrawn and she and her son eventually move away.
Six years pass, and Gertrude’s arm continues to trouble her as it becomes more and more disfigured. This is now her obsession, and it is one of the reasons for her marriage to Farmer Lodge going downhill. The marriage has been childless, and she blames the arm for making her less attractive to her husband. Another visit to Conjuror Trendle is called for.
This time he tells her that the only cure is for her to touch her arm against the neck of a man who has just been hanged. Despite the horrific prospect of having to get close to the corpse of a man fresh from the gallows, Gertrude determines that this is what she must do. The only problem is being able to do so in such a way that her husband cannot find out about it.
Although there were many criminal offences at the time for which hanging was the ultimate penalty, such events were relatively rare in a place like Dorchester, and Gertrude has to wait a long time before a suitable opportunity presents itself. When it does, she is fortunate in that Farmer Lodge announces that he will be away for a few days on business and, although she would normally be welcome to accompany him, on this occasion he must go alone.
Gertrude makes her way to the jail at Dorchester in secret and speaks to the hangman on the night before the hanging is to take place of a young man who had been involved in a rick-burning incident (this was a time of agricultural unrest in the English countryside and such events were not unusual). He tells her exactly where she must be in order to touch the corpse.
The following morning everything goes according to plan in that she is able to touch the neck of the hanged man and her arm is immediately cured. However, as she does so there is a terrible scream and, on turning, she sees Rhoda and Farmer Lodge standing there, having arrived to collect the body of their son, who is the boy who had been so much involved in the first part of the story. His offence had only been to be a witness of the rick-burning, although he had played no part in it (Hardy had been told about such an event by his father).
The story comes to a rapid end as the truth is revealed. Rhoda attacks Gertrude, announcing that “This is the meaning of what Satan showed me in the vision!” Gertrude falls insensible and dies three days later. Farmer Lodge, who had responded to Rhoda’s appeal when their son was arrested and supported her throughout, sells up and moves away, dying two years later. Only Rhoda survives to old age, having returned to her work as a milkmaid.
It is an interesting story, made more so by the slow build-up and swift denouement, but most readers will probably have worked out who the young man of “about eighteen years” will turn out to be. Some suspension of disbelief is necessary, but Hardy, as mentioned earlier, was convinced that he was retelling real events, combined with local folklore. How much is truth, and how much conjecture, is certainly open to doubt, especially given the fact that one of the characters whom he claimed to have met (Gertrude) would have died some fifteen years before he was born!
His description of the procedure surrounding a hanging at the Dorchester jail was based on his own experience of witnessing two public hangings there, although one was through a telescope from a distance of nearly three miles.