In the story "The Landlady" by Roald Dahl, the idea about strangers that applies is the danger of trusting someone you don't know. The protagonist, a young man named Billy Weaver, arrives in a new town and seeks accommodation at a bed and breakfast owned by the landlady. Initially, the landlady appears friendly and welcoming, but as the story progresses, it becomes clear that she has sinister intentions.
The story highlights the theme of deception and the dangers of blindly trusting strangers. Billy Weaver is lured into a false sense of security by the landlady's pleasant demeanor and the seemingly perfect condition of her bed and breakfast. However, it is revealed that the landlady has been preserving the bodies of her previous guests, and Billy becomes her next victim.
"The Landlady" serves as a cautionary tale, reminding readers to be cautious and skeptical when dealing with strangers, as appearances can be deceiving. It emphasizes the importance of exercising caution and not blindly trusting individuals we do not know well.