The Cain Saga Vol 5

From the VIZ Media edition

The death of Cain's would-be fiancée Emeline was only the beginning of the Lauderdale family troubles. Her mentally unstable brother Gilbert seems to have pulled himself together, only to discover that his father has also been brutally murdered. And just as Cain is drawn deeper into the family's mysteries, his own sister Mary disappears!

Source: Anime News Network Encyclopedia