Trick or treat means a Halloween threat to perform mischief on the homeowners or their property if no treat is given.

By putting Halloween decoration outside, homeowners signal that they are willing to hand out treats. So don’t be selfish and don’t turn your Halloween pumpkin the way only you can see it from your living room window.

On this photograph we can see a father giving last instructions to his older son about how to behave in public on Halloween (and what a lesson that was, I know, because I was there).