After finding the route to the lost city of Neruzavin, the adventurers must mount an expedition into the vast and deadly desert region called the Parchlands, where they hope to catch up to their treacherous former employer. They brave the deadly desert to arrive in an abandoned city at the edge of a lake where a Great Old One slumbers. The adventurers must track Count Lowls's party, recover a vile tome, activate the city's Star Stelae, and perform a powerful ritual that allows them to follow the Count to Carcosa. Along the way the characters must be careful they don't wake the slumbering Great Old One or stir up the flying polyps sealed beneath the city. What Grows Within is a Pathfinder Roleplaying Game adventure for 13th-level characters.