I guess, Uncle Roger, we must give "Ms. Ross" his due (some still don't know that he was a man and that was one of his pen names). He pumped out tons of paper from his typewriter (and I'll bet it was a manual) back at the height of gothic novels back in the early/mid-seventies. All the plots, whether they were DS or other-orientated, followed the same plot which you perfectly stated. He made lotsa moola doing that because the audience was out there.
I worked in our local public library during that gothic novel height and it had an entire section just for the books, most paperbacks. They all had the same cover: a spooky mansion in the background with only one window lit while some young, pretty thing in a nightgown was running away in the dead of night. By the late '70's, the gothic novel saw its collapse and in the '80's came the trend of "romance novels" about some young, buxom girl being wooed by a chesty, handsome, long-haired hero. Fabio gained fame as a model for the book covers which always showed him, bare-chested, holding on to the heroine with bosoms barely kept inside. It was common to make them period, especially in the 18th century, so she could suffer from some disease but eventually recover. They had titles like "Love's Wildest Dreams" and some-such. By the '90's, they had come and gone after flying off the shelf in bookstores and libraries. On an episode of The Golden Girls, Blanche tried to write one. She ended up with insomnia when she got "writer's block."
Gerard
