The Fringe season 4 finale is here! “Brave New World, Part 2” airs tonight, and all will (probably not) be revealed.

In the finale episode, which airs at 9/8c on Fox, the Fringe team is desperate to prevent a catastrophic event that could cause mass death and destruction. Leonard Nimoy is back as William Bell, and “it will end in a moment you will never forget.”

Watch the promo:

Share your theories in the comments, and we hope you enjoy tonight’s episode!