Hemlock is a young scholar invited to a crumbling castle in the Bohemian countryside. The wealthy nobleman Lord Fiodor Dornstein has hired him to translate a mysterious medieval book known as The Devil's Diary, a text rumored to harbor an ancient evil.

But when the book goes missing on Hemlock's first night, everyone becomes a suspect. In order to find the book, Hemlock will need to explore the castle grounds, question the local villagers, and unravel the secrets of a dark past.