James is exhausted running between Heston and Skeldale, and to make matters worse, he's often finding himself on the wrong side of Richard Alderson, who is miffed about the muddy floor. Meanwhile, Mrs Hall and Herriot are curious about what Siegfried's been up to when James finds him wandering home after a night out.

Skeldale House descends into chaos with the arrival of Siegfried's wayward brother Tristan. Helen provides James with a reason to stay in the Dales.

Siegfried hires an experienced bookkeeper, but her efficient approach doesn’t suit everyone. James and Helen arrive at a big decision, and a ferret presents a challenge for the practice.

When new vet Richard Carmody joins the practice, James feels his place by Siegfried’s side is threatened. Conflicts come to the surface at Mrs Pumphrey’s community tea party.

James needs a crash course for fatherhood. Mrs Hall referees between Siegfried and her new boss, Mr Bosworth, as they fall out over some of Mr Bosworth's safety tactics. Helen is concerned about the influence of Jenny's new friend Doris.

Everyone is determined to make Jimmy’s christening day special, while Siegfried is unimpressed when called up to Biggins’ farm.

Tristan and Carmody can't see eye to eye, but a quest to Pumphrey Manor might just bring them together. Helen tries to support James when unresolved feelings resurface.

James starts to behave out of character while examining Tricki, and his health takes a turn for the worst. Meanwhile, Siegfried, needing an extra hand in Carmody's absence, recruits a reluctant Tristan to help.

Fresh out of veterinary college in 1937, James Herriot struggles to find work in his Depression-struck home town of Glasgow. Seeking new opportunities, he pursues a position in the remote village of Darrowby working for eccentric local vet Siegfried Farnon, who is less than impressed by his early efforts. However, a difficult calving gives James a chance to prove his worth.

It's the Darrowby Show and James is pleased as punch that he has been given the honour of Attending Vet. But Siegfried and Tristan know the job is a poisoned chalice and reckon James won't last the day without throwing in the towel.

The fate of a struggling young widow causes difficulties for James and Helen's burgeoning romance. Meanwhile, Siegfried has another scheme to whip Tristan into shape, and a visit from Tricki Woo causes chaos in Skeldale House.

Everyone is trying to get along as best they can in the face of changes at Skeldale House. Helen has moved into the bedsit upstairs with James. James struggles to get Siegfried to let him take the reins now that he is a junior partner, and the pair clash when he learns how much money Skeldale could make from the Ministry of Agriculture’s lucrative bovine TB testing scheme.

James is finally succeeding with the farmers’ uptake of the Ministry of Agriculture’s TB testing scheme, but is struggling with the complicated paperwork - a fact that he is keen to keep from Siegfried. Tristan decides that he is outgrowing running the small animal surgery and buys a car to help with errands at the practice, which also provides him with transport for taking Florence, the daughter of Siegfried’s rival, George Pandhi, out on a date.

With World War II underway, Siegfried takes up the slack at the surgery. James faces an uncertain future when he is grounded at the RAF. Mrs Hall and Helen consider their contribution within the community, and Carmody is eager to step up.

James is forced to take in Mrs Pumphrey's pampered Pekingese. Tristan prepares to return to university, but needs Siegfried's help to pay for his accommodation, but Siegfried insists he must first prove he is serious about being a vet. James treats the Aldersons' prize bull, and Helen rewards his efforts with some unusual home baking.

It's an important day for Tristan in more ways than one, as he celebrates his birthday and Siegfried gives him new responsibilities as a vet. Tristan has to withstand the pressure and succeed in the challenge set by his older brother before returning to Skeldale for his birthday festivities. Meanwhile, Mrs Hall reminds James that he needs to tell Helen some home truths.

When a familiar face from Helen's past returns to Darrowby, James worries that he has to vie for her attention and steps up to compete against them at Mrs Pumphrey's annual cricket match. The rest of Skeldale House are apprehensive as the game can be brutal. Siegfried tries his best to train James and get a reluctant Tristan to step in, but it's not looking good for their Darrowby Eleven team.

It is now spring 1939 and a potential world war looms. Tristan is now a qualified vet, while James enters a new stage of his life with Helen and at the practice. After being made joint business partner by Siegfried, James pushes to take on more responsibility via the Ministry of Agriculture's new bovine TB testing scheme, but its unexpected challenges risk pushing him to breaking point.

It’s Easter 1940 and, with Tristan away, Skeldale House is busier than ever. Everyone looks to the future, and James tries to save a dog from its owner.

James and Helen are keeping a secret, and following a visit to the Crabtree’s Farm, Carmody is challenged with learning how to be a vet outside of his books. The new farmers have a worrying illness amongst their herd and James wants to help them in any way he can.

After receiving outstanding exam results, Carmody is offered a position in a research program in London, but he wants to stay at Skeldale. An exhilarated Mr Bosworth summons Mrs Hall to examine a piece of debris that has dropped from a plane into a remote field.

Tristan sets about collecting debts owed to the surgery and takes a shine to Maggie, the new barmaid at The Drovers. Siegfried hopes to bag the job of Attending Vet at Darrowby Racecourse, by buttering up the head of the race course, General Ransom. When the favourite to win on the race day is diagnosed with a inoperable condition, James has his first painful experience.

It’s spring in 1938, and a trip back home to Glasgow presents James Herriot with a dilemma that will mean choosing between the people he loves when he is offered a position at his old mentor's forward-thinking practice.

With Tristan's encouragement, James asks Helen if she'd like to go to the local spring dance. But village resident Gerald's arrival with his injured dog, Rock, puts a spanner in the works. Meanwhile, Tristan worries that Siegfried is in danger of losing his edge.

The Skeldale House regulars think about what matters to them most when the radio reports that Britain is standing on the brink of war. As everyone processes the news, James discovers a case of TB at Heston Grange. Richard begs him not to report it or the farm will be shut down and he could lose his livelihood.