When the Find-Outers investigate Banshee Towers, a reputedly haunted art gallery, they quickly discover the "ghostly wailing" is a hoax. As the friends delve deeper, Ern notices a crucial detail missing from a valuable painting. This clue leads them to expose a sophisticated art forgery ring, as they uncover a secret plot to replace priceless originals with fakes and sell them abroad, solving their final case.