Final answer:
The neighbors will likely start to suspect and accuse Les Goodman of being an alien due to the unusual spotlight at his house, evoking fear and panic.
Step-by-step explanation:
Based on the excerpt from The Monsters Are Due on Maple Street, it is most likely that the neighbors will start to believe that Les Goodman is an alien. The use of intense language, such as 'desperately frightened', and the focus on the spotlight as something out of the ordinary point towards a rising suspicion and panic among the people. Given the context of a dramatic television play, where suspense and conflict often drive the plot, this scenario seems to point towards an escalation of fear and the potential for scapegoating.