In their weekly preview, the producers of Gossip Girl give us a glimpse at the coming week's episode, "Raiders of the Lost Art," and tease what they are calling the biggest surprise of the season.

Executive Producer Joshua Safran, who is reportedly leaving the show to run Smash at the end of the season, is joined by his fellow writers in mapping out the third-to-last episode of Season 5.

Here's a sneak preview with clips from the installment, plus their commentary:

As we know, Chuck, Blair, Nate, Serena and Serena-Lite are teaming up to find Jack and uncover Diana's secret. This apparently results in some great comedic exchanges, and leaves Dan out in the cold.

It also gives way to the mother of all shockers as "Raiders of the Lost Art" concludes.

Says the episode's writer, Jake Coburn, "If you're a fan, you need to see the end of the episode, because it's going to forever change the landscape of the show, and you're going to want to see it for yourself."

Adds Safran, "Spoiler alert, this is probably the biggest surprise of the year."

What do you think it is?! Hit the comments below and tell us ...

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.