This week on All Creatures Great And Small, James and Siegfried realize that it’s very important to have an extra vet. James finds a vet student who needs to gain hands-on experience to come to Skeldale as his assistant. Mrs. Pumphrey’s foster dog and Tom Chapman’s horse will force the student to remember what he learned from the textbooks. Will he pass the test? Let’s find out.

The episode begins with Helen and James discussing how their busy schedules prevent them from trying for a baby. James tells her he’s found a vet student named Richard Carmody who can help. Helen is skeptical because James will still need to train him. Carmody arrives in Darrowby but ends up walking around in circles because the streets are so narrow. James believes Carmody is knocking on the door but it turns out to be Mrs. Pumphrey claiming she has an emergency. Her dire situation is her foster bulldog (possibly being played by a boxer due to current UK breed restrictions) Cedric having excessive flatulence. Mrs. Pumphrey is fostering Cedric after his owner was called up to serve. Carmody finally arrives, and his first encounter with Cedric results in Carmody immediately criticizing Mrs. Pumphrey for treating her animals like her children. James prescribes some medicine and a strict diet to rule out stomach issues as the cause of Cedric's woes. Mrs. Pumphrey then invites James to her garden party, but he plans to send Carmody instead so he can hang out with Helen while the others are away.

Meanwhile, Siegfried gets called up to the Chapmans’ farm. Diesel, Tom’s favorite horse, is wheezing more than usual. The audience gets to meet Tom’s mom Grace, who has moved back home to help out her parents. Grace is worried that Tom will return to find that his beloved pet has passed away. Siegfried believes Diesel may have a pulmonary embolism and tells Grace to reduce his exposure to hay and other potential allergens. He brings Carmody with him on the follow-up to see if he can put his assistant's brain to work. Carmody examines Diesel and determines that his lungs have improved. Carmody tells Grace the good news in medical jargon, and Siegfried has to prompt him to rephrase. On the way out of the Chapmans’ farm, they see a group of soldiers on a training exercise running across the fields. The soldiers open a gate and one soldier forgets to close it after the last person goes through. Siegfried warns the soldier to be careful because the farm animals can run away.

Unfortunately for James, his plan to escape Mrs. Pumphrey’s affair fails after she calls him to complain that Cedric still has a lot of gas. Instead of enjoying the fine, probably-breaking-rationing-orders food that Mrs. Pumphrey has catered, Siegfried, James, and Carmody spend most of the time arguing about whether Cedric just needs more exercise or if he has gout. While this debate goes on, Helen gets the impression that James doesn’t care about her because he’s spending more time doing vet work than husband's work, and she tells him she’s going home without him. Siegfried also gets a chance to talk to Gerald and they come very close to starting a friendship. Later on, Mrs. Hall and Gerald have a heart-to-heart about her anxieties over the divorce paperwork. He tells her to confide in him.

James believes the best way to correct Helen’s anger is to give her time to cool off, but Mrs. Pumphrey orders him to chase after Helen, so James ties up Cedric to go after her. On the way home, he sees that once again the soldiers left the gate open, and Diesel ran right into the sharp wooden edges. He goes back to the party to find Siegfried and Carmody to help save the horse, and James gives Helen another sorry look as they run off. Cedric seizes the opportunity of being unattended to knock down a whole table of baked goods and lick them all.

The vets find Diesel whimpering and scared. Carmody is struggling with how much blood is oozing from the site of impalement but he manages to help Siegfried and James pull the wood out of Diesel’s body. While the surgery is in progress Helen airs her frustrations with James to Mrs. Pumphrey. Helen also tells Mrs. Pumphrey that Cedric’s flatulence is likely due to his homesickness. Mrs. Pumphrey tells Helen that her own husband died young but brought her Tricki Woo’s great-grandma as her first dog. She advises Helen to forgive James for being so devoted to his career. Diesel survives the emergency surgery, but faces a tough recovery from the wound.

Carmody needs to learn more about “bedside manner”, keeping his thoughts to himself, and the rougher parts of large animal care, but he told Siegfried that he has no interest in signing up for military service. He feels that he’s more useful in helping maintain Britain’s food supply. Unfortunately, he also doesn’t know how to drive, which is a stumbling block to Carmody’s ability to take on the farm calls. He’s not completely scared off from becoming a vet yet, which is good, but he can’t rely solely on book knowledge going forward.

Grace is thankful that Tom’s horse is safe now, but she’s still afraid for Tom on the front lines. In this episode, Grace and Annie’s appearance isn’t just about keeping Tom’s memory alive while he’s away at war. The Chapmans also disrupt decades of period dramas erasing the presence of Black British farmers and land laborers on the home front. The “staying power” in the headline is not just about Carmody surviving Siegfried’s scrutiny. It’s a reference to Peter Fryer’s influential study of the lives of Black British people, especially those outside of London. Season 4 is committed to expanding the way audiences view who belongs in the British countryside.

Helen and James reunite and she forgives him. Helen notices that she’s been feeling tired and moody lately which may mean their plans for a family are starting sooner than expected! Who will teach Carmody to drive? When will the happy news of Baby Herriot be shared with everyone else? We’ll have to watch next week’s episode of All Creatures Great & Small to find out!