The horror movie technique of slowly building tension to a jarring shock which turns out to be something completely harmless and benign became known as a "Lewton bus" after a famous scene in this movie created by producer Val Lewton. The technique is also referred to as a "cat scare," as off-screen noises are often revealed to be a startled harmless cat.
The film was in theaters for so long that critics who had originally bashed the film were able to see it again and many rewrote their reviews with a more positive spin.
RKO executives were reportedly skeptical about the finished film, which they believed was too subtle and possibly not overt enough to compete with Universal's brand of horror.
Filmed in 18 days.
The film was such a hit at the box office, the releases of the next two Lewton films (Ho camminato con uno zombi (1943) and L'uomo leopardo (1943)) were delayed.