There always was a curse upon the Covenant family which killed them all either with a painful disease or drove them into madness. At the end of the 19th century the father of the current generation of Covenants reopens their old but abandoned mansion and thereby uncovers strange standing stones on an nearby island. Possessed by this discovery, he locked himself up in the library and wanted to uncover the meaning of those stones. Out of curiosity, in 1899 his three sons and two daughters stole a book about the stones out of his library, went to the island and conducted a dark and powerful ritual which marked the beginning of the end. During the following 20 years almost every member of the family either turned mad and killed themselves or died from something else.
Now it is the year 1923 and the very last member of the family, Jeremiah Covenant, lies on his deathbed with cancer in his body but he is not alone in his house. The spirits of his brothers and sisters haunt the house, strange events happen and evil creatures stroll through the mansion. In a final attempt to not only lift the family curse but also to put his fellow ancestors to rest, he calls upon Patrick Galloway. Patrick was part of his squad in the first great war and after a fierce battle against creatures, they had never seen before, he had specialised in abolishing such powers from the earth.
You take control over Patrick and walk around like in every other first person-shooter through the several locations of the game ranging from the mansion itself over other earthly locations to Oneiros and Eternal autumn, which are other plains of existence. On your way you uncover the mysteries of the family by reading books and papers which lie around the mansion or by talking to the few people still alive on the island.
Also reading might help you understand what is happening here, it won't help you survive against all the strange creatures that hide in the shadows and attack you without asking. It's also impossible to defeat the ancestral spirits without some serious firepower, so besides your trusty revolver, you'll also find several other weapons during the course of the game like Molotov cocktails, your lovely shotgun or a freeze gun shaped like a dragon head. Since you are fighting the paranormal, you also have access to several spells which allow you to see enemies before they see you, revive the dead or shoot Ectoplasm. Since you hold all your weapons in the left hand and you cast your spells with the right hand, it is possible to use both at any time.
As the name suggests, Clive Barker, the maker of the Hellraiser movies, had great influence in the making of the whole game. He also wrote the background story.