Planting a syringe full of anti-abortion vaccine into a farmer's backside creates something of a crisis for Tristan. Farmer Nat Briggs is convinced that his chances of starting a family have been ruined by Tristan's clumsiness, and he hangs threateningly around the Drovers waiting for a chance to confront Tristan. But it is Siegfried who gets a letter threatening court action. James, meanwhile, keeps Helen guessing about his mysterious visits to a local joiner, whose pet, Helen knows, died some time ago.

Tristan's heart is all a flutter because of the lovely Jane Mercer. When he discovers that she sings in the choral society, Tristan develops a fresh interest in matters musical. But strong-willed Jane takes a donkey's owner to task for neglecting the animal, much to the embarrassment of Tristan. Farmer Biggins, meanwhile, baffles all three partners with his strange behavior. A legendary non-payer of vets' bills, he finally meets his match when Granville Bennett - "the finest small animal practitioner in the north" attends his tom cat and manages to get Biggins to settle his outstanding account in full.

Tragedy strikes Bill Shadwell when his herd of dairy shorthorns contracts Johne's disease. As Shadwell approaches retirement, his son is keen to move into more profitable Friesian dairy cattle -- a move which means both James and Siegfried are caught up in the family's battle of wills. Mr. Grimsdale's bull poses problems of a different kind when Siegfried is convinced it has swallowed a dangerous metal object. But tightfisted Grimsdale is not convinced that an operation is needed. Tristan's new metal detector could prove to be the solution to a tricky dilemma.

The mysterious Mrs. Donovan poses problems for all three partners. Siegfried rashly dismisses her as "a warm-hearted woman who loves animals" -- until she starts interfering with his patients. From sheep to piglets, a howling dog to a hibernating tortoise, there seems to be no limit to her homespun remedies. Tristan has big trouble on his hands when cadging college pal St. John turns up looking for a bed -- and a small loan. Can Tristan keep St. John's presence a secret from Siegfried and the fearsome Mrs. Alton? Lovely Rosemary Brocklehurst attracts the romantic attention of Tristan when she brings in Esmerelda, a tortoise, which won't come out of its shell. Perhaps Mrs. Donovan has the answer...

Buffoon Stewie Brannen, an old friend of Siegfried's, has invited the distinguished Professor Norton to a black tie dinner, and prevails upon Siegfried to host it at Skeldale -- and lend him a dinner suit. But disaster looms when Siegfried and Stewie are called out for a calving, in full evening dress, and James has to hold the fort with an irascible Mrs. Alton.

There's unusual friction in the Herriot household when 12- year-old daughter Rosie announces that she wants to become a vet -- against her father's wishes. James goes out of his way to show her the arduous, dirty and dangerous side of his work, while Helen thinks he ought to encourage her. But treating her best friend's pony, which has tetanus, may prove too much even for the determined Rosie. Siegried, meanwhile, manages to lose Mrs. Pettinger's kitten Prudence, which escapes from the surgery and hitches a ride to Hull, causing consternation in Darrowby and mirth for Tristan.

Siegfried is determined to discover who shot Korean War veteran Jacob Pearson's dog. The suspect is Captain Crawford's willful and surly 20-year-old son, Hugh -- a young man with problems beyond his pompous father's control. Both James and Siegfried have extraordinarily little success in extracting payment from wily farmer Dennis Pratt -- until they discover he may be sneaking his cows onto a neighboring farm to enjoy better grazing.

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.

Siegfried is laid up at Skeldale with his foot in plaster. His dreams of mouthwatering meals prepared by Mrs. Alton are soon shattered by her regime of a strict diet "for an invalid". Tristan falls for the dark, sad-eyed beauty, Angela Mortimer, Mrs. Pumphrey's great-niece, who has been jilted by her fiance. Fortunately, the demanding dog Tricky-Woo provides an ideal excuse for Tristan to make a number of house calls. James impresses three hero-worshiping locals with his cow-curing abilities, and he learns to value their support when he has to judge the Darrowby Vegetable Show, with disastrous results.

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...