Night's Black Agents: Dracula Dossier
The Prosperpine is a mystery. It has been referenced and hinted at in numerous documents and the name whispered from the lips of more than one dying agent, but what it is, where it is or the exact nature is unknown.
Piecing together some evidence suggests it may be a ship, but the last official ship on the registry with that name was one that went aground in the very early 20th century. It is possible it is a prison, a research station or something else entirely.
The most concrete evidence suggests that the key to finding the Prosperpine may be in and around Exeter, UK.