The Countess and Marechal
"Shrinking House" opens with Jupter's Uncle Titus obtaining the belongings of a dead artist named Joshua Cameron. Shortly after the Joneses acquire these belongings, the sister of Cameron (The Countess) and her business manager Marechal arrive on the scene. They want to obtain Cameron's possessions for what appears to be sentimental reasons; however, before the mystery is over, the boys discover that the two are a pair of clever criminals who were working with Joshua Cameron in selling forged paintings.
The boys might never have suspected the two if Marechal had not decided to try to double-cross the Countess. He tries to steal Cameron's possessions before they are sold to Titus Jones, and he then hires Skinny Norris to help him examine paintings left behind by Cameron that reveal the location of a forged masterpiece. Of course, after the boys begin to suspect Marechal, it's only natural that the Countess may be guilty as well; so Jupiter is finally able to deduce the truth and unmask these villains, marking the first time that the boys' clients turned out to be the guilty party.