From huge dogs to tiny dogs, working dogs to lap dogs, hairy dogs to hairless dogs - the team investigates why this single species comes in so many shapes and sizes. Set in a typical English village, the team uses DNA science to reveal the sometimes surprising family trees of some of the village dogs. The team also find out how the extraordinary genetics of modern dogs underlies the extreme differences we see between breeds.

Historian Ruth Goodman uncovers the surprising origins of the poodle's famous haircut; finds out what makes greyhounds the fastest dogs on the planet; and travels to the Guisachan Estate in the Scottish Highlands to meet hundreds of golden retrievers at the ancestral home of this popular breed.

Steve meets the hairiest dog breed of all and reveals how its dreadlocked coat once acted as lightweight armour. Kate investigates the remarkable story of dogs - from their ancient ancestor the grey wolf, through thousands of years as our working companions, to the Victorian creation of the dog breeds we know today.