Sarah Burton returns to her childhood home after many years away to apply for the new vacant position of headmistress at the local school. Her personality wins over many people, but at least one of the school governors, Robert Carne, is against her appointment for reasons at first unclear. He is a landowner who recently lost the vote to become the new MP there, but Robert has his own troubles with a wife in a mental home and a daughter that has started to show signs of mental instability. He is just one of many people that Sarah Burton will encounter in the poverty stricken area of South Riding.

Sarah checks out her new school and teachers ready for the term to come, but is less than impressed by both the conditions of the building and the staff's lack approach to teaching. She also checks out the other pupils that will be attending there when she goes to a local stage production, where she encounters the Holly family, a family of nine who live in caravan type slums and who one of their daughter is rushed in to hospital with suspected appendicitis. The eldest daughter Lydia befriends the new neighbours Fred and Nancy Mitchell, who have had to move there when money became tight. While Nancy is snobbish about the area, Fred encourages Lydia's love for literature.

Sarah has her first meeting with Joe Astell, newly elected Alderman of the area at the local Jumble Sale and discovers they are like minds on many things. Anthony Snaith has hopes that his plan for the new road and development will go through, despite opposition from some locals, including former Alderman Robert Carne. But he has troubles of his own with his wife in a mental home and costs spiraling and things take a turn for the worst at the local hunt. Meanwhile councillor and vicar Alfred Huggins' sins come back to haunt him when Bessie Warbuckle has a startling revelation for him.

Sarah Burton is determined to secure improvements for her school building as term time begins and attracts the notice of councillor and vicar Alfred Huggins in her bid to gain funding. Pupil Lydia Holly is also gaining notice, especially for her school work, which rises hopes for Sarah as a possible promising pupil, but a sudden turn of events at home threatens those prospects. And a harsh winter for 1932 devastates much of the community, including local squire farmer Robert Carne, who Sarah finally meets properly when she is on hand to help when one of his cows goes into labour.

It's Easter 1933 now, and squire Robert Carne is reduced to selling the family heirlooms to make ends meet as his farming business continues to struggle. Sarah discovers why Lydia Holly's schoolwork has deteriorated when she learns that her mother has died and she is now having to raise her siblings. Determined to do something for a girl with promise she lobbies Mrs Beddows into doing something, but she is in for a surprise. Tom Sawdon, landlord of The Nag's Head, has bought his wife Lily and Alsatian dog to keep her company but she struggles to cope with it and goes to extreme methods in her way to get rid of it. And there is worse to come for South Riding when an outbreak of measles hits the community.

The measles outbreak continues to affect the community, with the young especially at risk. Fred Mitchell receives a letter from his old employer asking to see him, leaving to hopes of his job back, but while he leaves his wife Nancy's mother turns up to visit and try to persuade her to come home with her. Meanwhile Lydia continues to struggle to look after her father and young siblings, but sees a chance to visit her local dance class when going into town with sister Gertie, who has been sent home from school. She asks neighbour Nancy Mitchell to look after her youngest sibling while she is gone, little realizing that her actions could have grave repercussions.

Tensions and recriminations begin to run high at the school among the staff, while Sarah Burton looks at the possibility of laying off a couple of the staff. Agnes Sigglesthwaite, the oldest and longest serving there, lacks discipline in her class but surprises Sarah with her life story and past history. But Midge Carne has plans with the girls for a little game of her own that threaten Agnes' career. South Riding holds the annual fete, where Robert Carne hopes to win the show jumping cup for another year, while Sarah meets the enigmatic Anthony Snaith for the very first time.

Squire Robert Carne is stunned when he finds the bank will lend him no more money, while attempts to raise money elsewhere fall embarrassingly flat. But many in South Riding are struggling for money during the Great Depression. Fred Mitchell finds himself unemployed by his Insurance firm, much to his wife's dismay, who is even more distraught at the prospect of him putting in for Public Assistance to the local council. Barney Holly also finds himself without a job after pub landlord Tom Sawdon finally tires of his lax work ethics, but both later receive devastating news. And lay preacher Alfred Huggins receives an unexpected and unwelcome visitor as old sins come back to haunt him.

Mrs Beddows is disturbed to hear rumours that Maplethorpe may be sold while visiting the local asylum and goes to see Robert Carne. But she is equally perturbed to find School teacher Sarah Burton there when she arrives enjoying drinks. Later Sarah and Robert go out to dinner, but the evening proves a mixed one full of unexpected revelations. Alfred Huggins decides to court fellow members on the committee to buy property he secretly owns on the waste land tipped for the new road build, while Barney Holly decides to court the attentions of the widow Brimley.

It's Christmas in South Riding, but there is little in the way of festive cheer for some of the residents. Fred Mitchell receives a devastating loss when his wife leaves him to move back with her mother, leaving him near destitute. Robert Carne consults his doctor after collapsing during his date with Sarah, and later visits Mrs Beddows to ask her to be guardian for his daughter Midge if anything happens to him. Alfred Huggins, meanwhile, visits the Holly family in his unofficial role of Father Christmas, much to Lydia's discomfort, but her father has a surprise of his own for her. Huggins later visits Robert Carne in his continued efforts to get people onside to support the new road, but his bid to sway him backfires spectacularly.

It's now 1934 and Robert Carne is battling to hold on to his house and his seat in the local election against new candidate Stanley Dollan, a man backed by Anthony Snaith, who is suing Carne for defamation after implicating him in Alfred Huggins' property scheme. However, when Carne's aged farm hand dies he decides to hold his funeral on voting day in order to scupper Dollan's voting chances. Sarah Burton finally loses patience with Carne's daughter Midge, and later when Carne confronts Sarah over the building applications for the school the two clash. But later he disappears and one of the labourers discovers Carne's horse at the bottom of the cliff.

The search continues for Robert Carne as the authorities and community believe him dead. The press are intrigued as speculation grows that he either committed suicide or faked his own death due to his debts, and a reporter goes down to try and dig up some dirt on the story. Sarah is distraught, remembering their last quarrel, but she is not the only one grieving as Tom Sawdon's wife dies in hospital. Meanwhile there is a surprise twist in the road development, and Alfred Huggins day of reckoning comes when he confronts Anthony Snaith, who little anticipates Huggins' fury. And there is an unexpected visitor at Maythorpe Hall for Mrs Beddows and for Midge.

Lydia Holly has been accepted back into school, but her mind is elsewhere over her father's upcoming nuptials to Mrs Brimsley. However, an afternoon picnic with her siblings soon takes their mind off things when they make a nasty discovery. Meanwhile Sarah learns that Joe Astell is leaving for Glasgow, and Sarah clashes with Mrs Beddows over Robert Carne, leading to revelations for both women.