When a newly wed couple traveling in Hungary are involved in a traffic accident in which their driver is killed and the car is destroyed, they seek shelter and aid in the home of a strange and devil-worshiping "friend" (Boris Karloff) of their chance companion (Bela Lugosi). It turns out that Dr. Werdegast (Lugosi) has a score to settle with Poelzig (Karloff) and is looking for his wife and daughter after a long and enforced separation. But Poelzig is searching for a fresh human sacrifice to Satan and sees the young bride as perfect for the task. There are a few twists in the plot from this point on, which I won't reveal here, but they do add interest to the film (even if somewhat predictable).
The Black Cat, like the Raven, is named after Edgar Allan Poe's writings, but has very little to do with its namesake. The only reference to a black cat in the movie is Werdegast's phobia of them, and really, this could have been left out without affecting much of the plot or overall effect of the film.
That said, I still enjoyed this film, especially because of the acting and dialog between Karloff and Lugosi. It just seemed to real and so perfect. The plot was a bit thin, but entertaining nevertheless. The setting was very different from the old castle settings of Frankenstein and Dracula, but its modern feel (I'm sorry I know little about architecture and interior design) still managed to carry a menace and dark atmosphere that was very appropriate.