“We’re gonna put together a show unlike any other show that anyone has ever seen,” Backstreet Boys resident blond Nick Carter shares in the promotional video for the upcoming performances.

But where the element of surprise does come in is what you do with that Vegas spot — and the Backstreet Boys were clearly ... And once the curtain was drawn, well, then the nostalgia party ...

The Backstreet Boys 2015 documentary is necessary viewing ... but simply pulls back the curtain for you to glimpse the downside to owning the top of the charts. It’s not so much a cautionary ...