The fourth season of All Creatures Great and Small will pick up in springtime of 1940 with change on the horizon for everyone in Skeldale House. James and Helen wonder when the right time might be to start a family, not knowing whether or not James will be called up to serve in the RAF. Tristan’s absence is felt by all, but no one more than Siegfried who attempts to hold the growing household, and himself, together as he braves this new world. Mrs Hall and Helen’s friendship blossoms as they look to the future and new trainee veterinary student Richard Carmody arrives, causing complications in the house.