Okay, look. There are two ways that a series finale can go. It can tie everything up in a satisfying way or it can just keep limping along and end with a big cliffhanger that everyone knows will never, ever be resolved. And if The Event is anything, it’s a show that loves cliffhangers it can’t resolve.
So! The superteam of Sean, Simon, Sterling, and Vicky manage to get two of the planned virus releases shut down, even though Martinez isn’t officially back in the presidency yet. They also manage to kill Carlos and corner Sophia in the Air Avias lounge. But then Martinez manages to become President Martinez again by recording Evil Vice President Jarvis’s poorly timed confession. So all the flights out of Dulles get shut down and Sophia lets herself get arrested without even releasing her virus.
So that means it’s time to throw some unsurprising plot twists at us. So, in fairly rapid succession, Leila reveals that she’s pregnant with some sort of one-quarter alien baby, then the giant portal opens and brings the entire alien planet over into the sky above DC, and then Christina Martinez turns out to have been an alien all along. Just like I said!