From the back cover:
"An ominous encounter with a fortuneteller sends a party of adventurers on a 200-mile journey across the Lands of Intrigue. While traveling through the towns and terrain (detailed here for the first time) that lie in their path, they hear rumors and obtain clues about their mission. Their ultimate destination is Castle Spulzeer, a once proud stronghold that has become a den of terror.
When the heroes enter the haunted keep, they meet a terrifying trio of residents: a madman armed with stolen magical power, a lich whose secret laboratory houses untold horrors and treasure, and a furious ghost bent on revenge. These three ensnare the party in their fight over an ancient weapon. Each will stop at nothing to keep it from the other two. The heroes must choose with whom they will ally - and the wrong choice could lead to their doom.
Castle Spulzeer is an adventure complete in itself. However, as a crossover story, it offers every Dungeon Master a choice between two endings. The first leaves the part in the Realms. The second transports the characters to the Demiplane of Dread where the plot continues in the RAVENLOFT adventure The Forgotten Terror."