Elizabeth Berger and Isaac Aptaker drop intriguing clues about the last episode of season 4.

What hath Randall wrought?

“There will be fireworks,“This Is Usexecutive producer Elizabeth Berger tells EW.

This Is Us

Ron Batzdorff/NBC

“I think we can promise fireworks between the brothers.”

One can only speculate which old new friends might pop up.

“There are familiar faces and there are also some new faces,” hints Aptaker.

“We tried to do something this year a little elegant, where we framed the season with strangers.

Moving from through-lines to timelines, how many eras will viewers visit in the finale?

“A lot,” teases Berger.

“We’re all over the place in this one.”

Hold on to your hats, and probably your emotions too, as the Pearsons enter unusually charged territory.

“Things are really fraught in our family in this one,” Berger warns.

“I keep going back to the wordexplosive.

I do feel things are unusually explosive for our family at this point.

I think people are going to be pleasantly surprised by where the hope comes from in this episode.”

As usual, though, for every mystery answered, another will crop up.

“Strangers: Part Two” airs Tuesday at 9 p.m. ET/PT on NBC.