This is perhaps one of the best "Twilight Zone" episodes of the entire series. The beginning is mysterious, and though confusing, it gives you a big clue as to what will follow. It starts with the end, and does a flashback to what got the main character there. As the story unfolds you forget how it began. Those big tall aliens, who left the book at the United Nations are frightening to look at, but the wonderful things they are doing for the people of the Earth make them seem completely benevolent. It had me and my brother fooled until the end, when the woman ran up and shouted out those three unforgettable words, "It's a ....". No, I can't tell you what she said, you must watch it for yourself. When you do, I think you will add this film to your Sci-Fi Hall of Fame!