Переполох в отеле «Гранд Метрополитен»

The story's resolution feels so satisfying and unexpected. I wonder what inspired the puzzle at the heart of this mystery.

It moved quickly but gave enough detail to keep me engaged without feeling rushed. Is that typical of Christie's short stories?

His attention to detail and psychological insight are so distinctive. Do you think this story showcases his classic detective style best or offers something new?