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.