It's about a group of siblings who overhear that their family's "fortunes have fallen," so they decide to restore them by various get-rich-quick schemes: digging for treasure, going into business, rescuing wealthy old men, etc. All plans work about as well as you'd expect, most get them in trouble, some nearly kill someone. What makes it great is the narrator's voice and the author's distaste for moralizing. It's a hoot.