In this satire of the DaVinci code, when Homer briefly leaves Maggie outside a convent, the nuns take her in and refuse to give her back. Trying to recover her sister, Lisa uncovers a plot involving a mystical gem, the founding fathers, and Principal Skinner's mother's minivan.In this satire of the DaVinci code, when Homer briefly leaves Maggie outside a convent, the nuns take her in and refuse to give her back. Trying to recover her sister, Lisa uncovers a plot involving a mystical gem, the founding fathers, and Principal Skinner's mother's minivan.