In the final episode, Judy Puddifoot investigates the warning signs dogs give out before becoming aggressive, and Steve Leonard looks into the latest research that suggests feeding your cat only fish-based pet foods over the long term could lead to health problems. Elsewhere, Alice Rhodes discovers that one in five cats in the UK lives in a state of long-term anxiety because they share a house with another cat, and she runs a series of unique experiments to test different stress-reducing methods. Last in the series.