Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
Set in Ireland of the 1920's, players take on the role of Patrick Galloway, who has been summoned to an ancestral estate by its lone descendent Jeremiah. Death has claimed his four siblings, each who have reanimated intent on slaying their living brother, the last of the family, so as to free the Curse of the Undying King.
In order to save his friend and unravel the curse that has befallen Jeremiah's family, Patrick must embark on five perilous quests before he can unearth the final horror of the estate.
Each quest brings Patrick face-to-face with one of Jeremiah's undead siblings and the strange and wicked creatures the curse has attracted. In addition, Patrick must triumph over his reviled competitor Kiesinger. If there is power to be had by unearthing the mystery of the estate then Kiesinger will try and steal it - and there is much power to be had. It's up to Patrick to defeat each of Jeremiah's siblings and vanquish Kiesinger in order to quell the Undying King.