From the back of the book:
The family Stross ruled Zobeck with ruthless cruelty and shadow fey magic for nearly 600 years—until those who suffered under them finally reached their boiling point. The ensuing revolt overthrew the hated Stross and left their cursed castle a dark and shunned place.
Return to Castle Shadowcrag is an adventure where past and present mingle. As the players explore this legendary castle, a single step can send them back in time to participate in its most important events—and possibly change history. Can they lift Shadowcrag's curse, sever its connection to the Shadow Realm, and redeem its melancholy steward, Evander Stross?
The adventure is intended for four 11th-level characters or five 10th-level ones. The heroes are expected to gain 1 level before the adventure's climatic ending.