Not at all like the original story

This film is somewhat based on the original story of same name by August Derleth.
It's far from being a completely faithful adaptation.
If they made this film like the story it might have turned out to be a better
Horror film than it was.

For one thing the story was about a family secret involving the relationship between the Whateleys and the Marsh family 1st mentioned prominently in Lovecraft's story Shadow Over "Innsmouth".
The Marsh family it turns out had some strange ancestry involving miscegenation
or sexual involvement with a race of marine amphibious or (to use Lovecraft's favorite adjective "batrachian") race of beings.
Creatures that resemble the creature from the black lagoon.
In Derleth's story "Shuttered Room" one of the Whately women goes to Innsmouth
and encounters one the Marsh family members.
They get personal as in intimate and the rest becomes a sordid history.

The result was that this also became part of the Whately legacy as well.
How the Marsh family encountered these amphibious creatures and how they got
involved with the strange esoteric order of Dagon ( the religous cult featured
in the Lovecraft stories ) is another lengthy story in itself.
For those interested in knowing more I recommend reading Lovecraft stories especially "Shadow Over Innsmouth".
That one story alone tells the whole history of Innsmouth and the Marsh dynasty.
Derleth's story "Shuttered Room" while not exactly a sequel does spin off from
this.

Also this would give you an idea of what horror really was in that shuttered room and that decrepit abandoned mansion.


Maybe this world is another planet's Hell. - Aldous Huxley (1894-1963)