The Event:
…new fall show showing up on TV this fall. This is totally a guess, but my take is that sometime in the recent past, a group of around 50 scientists came to ‘our’ timeline from an alternate one that was more advanced than ours - similar enough to communicate well, but the difference / advancements were SO different that the Powers That Be don’t dare let them out in our world. Too disruptive, etc.
Also, no idea if the alternate history line could reveal some big gotcha secrets that the Powers That Be don’t want to get out, like contact with alien races, who won the Preakness next year, or something else.
Again, all a guess.