Jason O'Mara, Stephen Lang Jason O'Mara, Stephen Lang

Don't expect the season finale of Fox's Terra Nova to end with a bang — it starts with one! Airing December 19, the two-hour episode kicks off with the colonists warily awaiting the arrival of the 11th Pilgrimage. They're not sure if this is good news or bad. Bet on the latter. "Our evil guys, the Phoenix Group, will send somebody through the portal with a bomb, and it explodes," says exec producer René Echevarria. "Jim Shannon [Jason O'Mara] is hit by the blast and wakes up three days later to a very surreal scene — Phoenix soldiers have taken command of the colony."

This will eventually force Shannon and Cmdr. Nathaniel Taylor (Stephen Lang) to do the unthinkable. "We have supercharged the premise of our show in a very chilling way," says exec producer Brannon Braga. "Everything changes."

The jam-packed closer also includes an unexpected return to 2149 and a head-scratching discovery that will leave the colonists — and the audience — rethinking the space-time fracture that connects the future with the past. And prepare for the demise of two notable characters, including one who has become quite a fan favorite. Hints Braga: "A person who is without family will willingly go to [his or her] death in order to help the Shannons survive."

Also expect the turmoil between Taylor and his son, Lucas (Ashley Zukerman), to hit full boil. "We know Lucas has been helping the Sixers and the Phoenix Group, and we've teased that something bad happened between the two men in Somalia, but we don't yet know why Lucas so intensely hates his father," says Echevarria. "That will all come out in the finale. It's Shakespeare meets Sophie's Choice."

For more scoop on your sci-fi favorites, including Fringe, Supernatural and Doctor Who, pick up the new issue of TV Guide Magazine, on sale Thursday.

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