Uncle Silas by LE FANU, Joseph Sheridan

Uncle Silas is a Victorian Gothic mystery/thriller novel by the Anglo-Irish writer J. Sheridan Le Fanu. It is notable as one of the earliest examples of the locked room mystery subgenre. It is not a novel of the supernatural (despite a few creepily ambiguous touches), but does show a strong interest in the occult and in the ideas of Swedenborg. (Summary by Wikipedia)