From the front of the book:
The kingdom of Cormyr is cursed. Prophecy warns that the Queen of Thorns will end the reign of the Obarskyr family and take the throne for her own. Dare you stand with King Foril in his attempt to defy this terrible fate? A Living Forgotten Realms adventure set in Cormyr for characters levels 17-20. This adventure can run long; we recommend that you allow 5-6 hours of play time, but some groups have completed it within a standard 4–hour slot.
This adventure concludes the Major Quest started in CORM1-6 Curse of the Queen of Thorns (P1) and continued in CORM2-3 Secret of the Queen of Thorns (P2). Players are strongly encouraged to play the three parts of this Major Quest in order, with the same character, if at all possible. Story Awards from the previous adventures have a very strong influence on the details and difficulty of this adventure.