Siegfried’s respect for animals was instilled long ago. As an officer serving in Belgium during World War I, he witnessed a comrade succumb to a gas attack while trying to save a horse. “The animal always comes first,” the soldier said.
During that doomed mission, Siegfried and another soldier, Maurice, managed to save a downed horse and eventually nurse the animal back to health—only to be ordered by their superior Major Saunders to kill it, and all the other horses that have carried them into battle. The war is over, and transporting all the animals back to England would be too costly, so they will be sold to the French and Belgians as meat, and they’re easier to transport dead. Siegfried personally shot the horse he saved. Saunders’ horse got to live, and be personally escorted back to England over the Channel by Siegfried.
Now Siegfried is once again seeing to a horse of Saunders’ that has endured a sea crossing. Saunders bought the horse, River, with the intention of racing it, but it’s skittish around people and bucks off anyone who tries to ride it. There’s nothing physically wrong with River, but Siegfried wants to address the psychological problems. He manages to calm the horse by catching eye contact, and, after a day of work with River, promises to return the following day. Repairing the damage will take time, and he refuses to rush things despite the pressure of Saunders and his stable manager Monkham.
Siegfried’s patience with River doesn’t carry over to the humans with whom he lives and works. He orders Tristan to clean and organize the dispensary when he finds poison next to antiseptic, and even complains that James and Helen are messy. Siegfried seems preoccupied by thoughts of his time in the military, poring over a recent letter from Maurice. It’s made him “rather combustible,” as the others put it.
Tristan completely overhauls the dispensary, to Ms. Hall’s delight—she makes sure to tell Siegfried. But he also buys a new sedative from the practice’s chemical supplier of which Siegfried is skeptical. Nevertheless, he agrees to try it on River, on Tristan’s suggestion. Helen wants Tristan to take on more work, thus sparing the exhausted James, who has been out on call several nights in a row. She breaks an unspoken alliance against Siegfried by revealing Tristan’s hiding location when he’s trying to avoid his brother. But when she suggests that Siegfried give Tristan more responsibility, Siegfried snaps at her. Mrs. Hall, suspecting he has been dwelling on his past, assures everyone his orneriness will pass.
Helen also wants James to stand up for himself, both with Siegfried and with clients. An older woman, Mrs. Beck, has bullied James into spaying her cat for a lower fee. When he and Helen pick up the cat for the operation, it gets loose in the car and scratches them both up. They happily give it to an over-confident Tristan for the operation, and laugh as they hear a commotion from the surgery. Tristan’s new sedative clearly doesn’t work very well.
When Helen and James return the cat to Mrs. Beck, Helen experiences firsthand the difficulty of standing up to her: she weasels her way out of paying then, insisting she will do so at the follow-up appointment. But Helen does get to witness James’ backbone in his dealings with the farmer Cranford. One of Cranford’s cows has died, and he insists it was struck by lightning, despite all evidence—that way he can get an insurance payout. But James refuses to falsify documents, and certifies the cause of death as a disease after a postmortem.
Later, at the pub, Helen agrees to help Tristan dodge Siegfried’s wrath by pretending that the sedative works—they must present a united front against him. Meanwhile, Cranford starts inveighing against James and his plans to test farms for tuberculosis. James launches into a spirited defense in front of all the farmers gathered in the pub, and Helen comes to his aid, despite her own misgivings about the testing: if one cow turns up positive, a farmer might lose their whole herd, and the government doesn’t compensate them enough. But James knows that TB-infected milk could kill people.
Cranford turns to Helen’s father and asks if he’ll be testing his herd. Helen has asked him to consider it, on James’ behalf, and he decides then and there to go through with it, telling all the farmers in the pub. James is relieved. Siegfried continues his incremental treatment of River, saddling the horse and riding alongside it before eventually trying to ride River himself. He has determined that River’s fear stems in large part from riding crops—and when Siegfried is successfully riding River, Monkham signals a stable hand to brandish a crop. Monkham doesn’t want to be proven wrong in his thought that River can’t be fixed. River bucks Siegfried off.
Saunders decides to put River down; a racehorse that can’t be ridden isn’t worth the cost. Thinking back to the war, Siegfried stands up to Saunders and tries to appeal to a sense of humanity. But Saunders has seen too much horror in the war to believe in humanity. Back at Skeldale House, Siegfried opens up to Mrs. Hall, explaining that Maurice has committed suicide. Siegfried recently had a letter from him, and he seemed happy—but Siegfried worries that he missed something and could have helped him.
The next morning, Siegfried is conciliatory and apologetic to everyone for his recent behavior, especially towards Helen. He realizes from the scratches on everyone’s faces that Tristan’s new sedative doesn’t work, but calmly dismisses it. He then asks Tristan to drive him to Saunders’ estate, to put down River.
On the way, Tristan asks his brother if he’s alright. None of us is, given the state of the world, Siegfried replies—but Tristan is blissfully ignorant and happy. He offers to start taking on night calls, and Siegfried agrees to install a phone in his room that very day. As Siegfried prepares to euthanize River, a stable hand walks in with a crop, agitating River. Siegfried decides that he can’t give up on the horse, and insists on helping it recover, slowly, over time. He didn’t help Maurice, but he can help River. He saddles up the horse and rides free across the dales.