England is at war and the time has come for James and Siegfried to join their military units. Their last day at the practice is a busy one and James is repeatedly called out when he had hopes to spend a last, quiet evening at home with Helen. Siegfried surprises James with a small gift. Mrs. Hall also has a surprise announcement for everyone and Tristan receives shocking news from the Royal College of Veterinary Surgeons.

Christmas at Skeldale House can be a formidable undertaking, what with sick foals, overfed dogs and a skeleton guarding Siegfried's secret hoard of goodies.

It's raining cats - literally - when Tristan has to face the terrors of an enormous sow, Our Gracie, and her litter of piglets, who are due to be castrated. When the farm cats take a fancy to the anesthetic-stuffed offcuts, they start to doze off in some very unlikely places. Mrs. Clarke, a very determined old lady, is struggling to keep her farm running until she can hand it over to her young granddaughter, Mary. But she is reaching the stage when she can no longer handle the pressures, even with her elder granddaughter, Katherine to help -- and Katherine is planning to pursue a nursing career in Africa...

Siegfried discovers that a gift given in good faith has brought the deadly foot-and-mouth disease to the dales, and James accidentally hits upon a "sleep cure" for Mrs. Flaxton's poodle.

Life at the Yorkshire veterinary practice continues to challenge the partners, whether by neglected animals or tight-fisted farmers. There are domestic challenges for Tristan, however, when James and Helen play a practical joke with a "Welcome Home" card from an old female admirer. Life is never simple when true love or the demon drink rule Tristan's life, and he is soon in trouble with Siegfried. A new housekeeper, Mrs. Alton, has been recruited by Siegfried to keep a watchful eye on Tristan, who, dispatched to tie up the details of her employment, is delighted to discover that Mrs. Alton is a rather attractive young widow. But this is not the Mrs. Alton that Siegfried had in mind.

Siegfried takes a close friend to task for wasting his own talents as a veterinary surgeon. Ewan Ross -- "the best horse man north of the Humber" has let his career slide gently into the whiskey bottle after the death of his wife. But Siegfried is determined to make use of his considerable skills. A valuable racehorse with a strangulated hernia could provide Siegfried with not only a way of striking back at "vets in Bentleys", but also putting Ewan on the straight and narrow. James, meanwhile, is strangely reluctant to take on responsibility for Mrs. Pumphrey's beloved Tricky-Woo when she announces that she is off to France. But Siegfried caves in under the persuasive skills of Mrs. Pumphrey and Tricky-Woo moves into Skeldale.

James' temper is fraying fast -- what with two car accidents in the space of a week, an inauspicious meeting with Helen's family and his rival still lurking around Helen like a "big glossy spider".

The fortunes of the hard-working Dalby family look set to dwindle even further until almost by accident James discovers the cause of their herd's illness. However, James still needs a push start on other fronts, and Siegfried and Tristan decide to remedy matters with their own expert advice.

Having failed his exams, Tristan fears his brother's wrath. In a desperate effort to reform, Tristan shuns cigarettes, alcohol and women and adopts a rigorous routine of dawn runs and hard work.

The waiting room is packed at the Darrowby practice, but Siegfried seems more focused on catching his hard-drinking brother asleep on the job.

As the tractor threatens to do away with a way of life in the Dales, James battles to save a dying shire horse.

Siegfried bumps into Mr. Beresford, the manager of the local bank whose dog behaves badly in the car. Tristan woos the lovely Marjorie Simpson and Siegfried meets Sarah Raworth. James treats the elderly Mr. Bailey's dog who has developed a bad case of bronchitis and Siegfried criticizes James when he waives the fee. Siegfried, however, has trouble following his own advice. Tristan rescues a severely injured cat and then convinces James to treat him rather than put him down. Helen promptly adopts him and nurses him back to good health but is devastated when she learns the cat belongs to the Gibbons family. Everyone celebrates Tristan's birthday.

Tristan has had a rather late night and Siegfried takes him to task over his bad habits. Tristan announces that he has a steady girlfriend, Deborah Mount and will reform his wild ways. Turns out Deborah's father doesn't know anything about the relationship and may not approve. When he does hear of it, he has serious doubts about Tristan's character. Tristan doesn't help his case with his silly pranks. James has several encounters with a street urchin, Wesley Binks, whom he'd earlier caught stealing. James nonetheless helps Wesley out when his dog contracts distemper. Siegfried reacts badly when the Weeting brothers tell him they are off to join the military.

The Herriots prepare to move to Rowangarth and another emergency with Granville Bennett.

James meets a pair of elderly twins. Oliver and Roland Strong, rabbit breeder and prize cabbage-grower respectively, have divided the cottage left to them by their mother and have not spoken to each other for 50 years. Now Oliver is convinced that Roland has poisoned one of his rabbits.

Siegfried is perplexed when the usually-caring Grandma Clarke snubs her neighbor, Franco Pedretti, who is the new shepherd on the estate where she is a tenant farmer. It soon becomes apparent that she blames Franco for the untimely death of her son in Italy during the war and the subsequent death of his wife in childbirth.

Sigfried declares that the business is in shambles financially, and his solution is Miss Harbottle, a meticulous secretary who rules the cash box with an iron hand. Amid a relentless succession of new faces - many gruff, some eccentric - James meets the lovely Helen Alderson.

The sport of kings beckons James and Siegfried to the Broughton Races — James in search of a dead cert to raise forty pounds for a Mediterranean honeymoon, and Siegfried in pursuit of a dream job at the track.

The return of lambing season brings a boost to Siegfried's spirits, but James, laid up in the surgery, is reminded of the harsher realities of a vet's life.

Nerves are frayed as Tristan's encounter with an "exploding" bullock leads to a lawsuit, and Siegfried's venture in guinea raising runs foul. Meanwhile, James is sent to assist "on of the biggest boozers in the business."

The Darrowby Show is a much-anticipated event for the whole community, except for the duty vet. This mixed honor falls to James this year.

The atmosphere is tense as James prepares to perform groundbreaking surgery. Meanwhile, Siegfried wrestles with a disinterested prize bull, and Tristan's hormones run riot over Darrowby's merry widow.

Tristan and Siegfried meet Roddy, a hobo and his dog who are passing through the area. Mrs. Hall needs to visit sick relatives for a few days and Tristan is assigned chief cook and bottle washer. He also has to do the spring cleaning, cook the meals and put in his time in the surgery. Siegfried is less than sympathetic when Tristan complains. Granville Bennett stops in wanting the vets to care for his dog, Phoebe, who needs an minor operation. He invites James and Siegfried to lunch the next day and James once again over imbibes. Helen practices her first aid skills on James.

James and Helen are about to celebrate their first wedding anniversary and Tristan suggests to James that they go to the Harlequin, a modest restaurant that opened recently. It turns out to be anything but and is in fact one of the poshest restaurants in the area. Siegfried starts seeing Margery Egerton. Tristan, now a free man since being forbidden to see Miss Mount, sets his sights on previous conquests. Siegfried and Tristan ask James to arbitrate when they both want the same evening off. James has to pay several visits to Mr. Bailes whose dog seems to take great delight in scaring the wits out of him.

When James treats a sick cat, he finds himself in an awkward position with Mrs. Pumphrey and Mrs.Tibbett. These two formidable and mutually ferocious Darrowby matrons compete both in presents for the invalid and in hounding James for information of the patient's progress.