For over two years the Humane Society of the United States conducted the most comprehensive, in-depth investigation ever undertaken of large-scale commercial dog breeders known as "puppy mills."  Its primary target -- the largest puppy-selling retailer in the country, Petland. 

ANIMAL PLANET INVESTIGATES: Petland takes viewers undercover and into the core of the horrific puppy mills that are suspected to be key suppliers to Petland. We follow undercover investigator "Mike" as he crisscrosses the state of Oklahoma and talks his way into dozens of breeders who sell puppies to Petland.  With his hidden camera he gives viewers an unprecedented look inside. 

We also meet meet consumers who have purchased sick puppies from Petland and a former Petland vet who blows the whistle on the company..