By Emily Rome
July 29, 2013 at 11:00 AM EDT

The heroes of Falling Skies fell to some new lows in Sunday’s episode as the Espheni mole found a way to shake Charleston to its core — literally and figuratively. On the alien invasion series’ post-airing talk show, 2nd Watch, Wil Wheaton leads a discussion about this latest episode with Drew Roy (Hal), Sarah Carter (Maggie), Doug Jones (Cochise), Seychelle Gabriel (Lourdes), and showrunner Remi Aubuchon.

SPOILER ALERT: Don’t read on if you don’t want to find out what happened on Sunday’s episode of Falling Skies, “Journey to Xibalba.”

In the episode, the Charleston survivors’ fight against the invading aliens takes a major blow when the nearby Vohm compound is destroyed and when Lourdes — controlled by an alien parasite — plants a bomb in Charleston that kills several of its inhabitants and traps more underground.

Check out the newest 2nd Watch video below for discussion about keeping secret the true identity of the mole, what Cochise goes through in this episode, and which Falling Skies character Wheaton has a crush on.

The season 3 finale of Falling Skies airs on TNT on Sunday, Aug. 4 at 10 p.m. ET/PT.