[Character]'s relation was murdered, but no one knows how, by whom, or why. Their body was a mess and only identified with a DNA test. [Character] inherits an envelope which contains a map/letter/photos. The envelope was sealed a hundred years ago, but the map/letter/photos appear to lead [character] on a journey which unravels the mystery of their relation's murder.
Possible plotlines: -Their relation was a scientist, trying to figure out how to time travel. -Their relation was involved in a cult. The map/letter/photos are related to a sacrificial ritual, planned a century ago but only just carried out.