The family surname central to Lovecraft’s “The Lurking Fear” is Martense. The story’s mystery leads the narrator to the isolated Martense mansion on Tempest Mountain, where generations of the family have withdrawn from ordinary society.
The mansion was built by Gerrit Martense, a wealthy New-Amsterdam merchant, in 1670. His descendants become increasingly insular and intermarry with people living around the estate. The family’s history includes the suspicious death of Jan Martense, who is believed to have been murdered after returning from military service and becoming estranged from his relatives.
The narrator eventually discovers that the horror haunting the mountain is tied directly to the Martenses. Centuries of isolation and inbreeding have transformed members of the family into grotesque, ape-like underground creatures. “The Lurking Fear” was written in 1922 and first published in Home Brew in four installments during 1923. The names Jermyn, Marsh, and Whateley belong to other Lovecraft stories, not this family mystery.