The Puppy Club are back in Sleuth City. There's been a major theft from the biggest private art collection in the city. Surrounded by high walls and swarming with guard dogs, the girls can't work out how the thieves did it. But the Mystery Pups' super skills are soon at work, and when they find a mysterious parcel in the attic, the girls are curious. Could it be that the multi-million dollar painting hasn't been stolen after all?