So I am having something of a Gothic week already, having read The Castle of Otranto by Horace Walpole (again) and watched two Laird Cregar thrillers, The Lodger and Hangover Square. These things are all Gothic in different ways, the films in the latter sense of the term, the novel as the point of origin for that term being applied to literature/narrative in the first place. I can't read Otranto these days without taking the long view of Gothic; it's quite a feat that Walpole accomplished with one wacky little book.
The plot of Walpole's story involves a bunch of attractive youths (Theodore, Isabella, and Matilda) running around a spooky castle and trying to thwart the grandiose criminal schemes of an older bad guy (Manfred, who also happens to be Matilda's dad). Ghostly paintings come to life, skeletons utter dire warnings, and giant people parts appear and disappear all over the place. There's a curse, naturally, and a lot of scenes involving dark passages, mistaken identity, and secret doors. The only things missing are the stoner dude and the dog, and the whole thing would work great as an episode of Scooby Doo, which is, of course, actually authentic Gothic in the sense that it basically follows the plot directives of Walpole's immediate heir, Ann Radcliffe. Radcliffe always explained away the apparent supernatural at the ends of her novels ("...and the Creepy Creature is really just Old Man McGrumpus!"), but Walpole goes for the full supernatural effect as well as an impressive body count. Still, he's setting up the conventions that later Gothic texts of various kinds, from The Mysteries of Udolpho and Jane Eyre to Dark Shadows and Buffy the Vampire Slayer, are going to employ, albeit in sometimes altered and even ironic forms.
Bedlam, which stars Boris Karloff as the keeper of the infamous 18th century madhouse. I'd suggest reading The Castle of Otranto if you really want to get what the whole Gothic thing is about, but for movie buffs the Lewton picture sums it up quite well. The picture shows Anna Lee as the film's heroine, who finds herself falsely imprisoned in the sinister asylum. It's a perfect snapshot of the Gothic idea.