The Stranger Who Shows Up At Your Door??

I love Halloween, but have to admit that it was a ton more fun when the kids were little.We shall be completely settled by the time we move into our house by this time next year so I just might throw a Halloween party! And your writing scenario today is about what you would do if a young woman showed up at your door wearing this costume. It looks harmless enough. Would you take the chance and let her in? Hey, it is a Halloween party. She might simply have been invited by a neighbor?? What would you do??