Changes are afoot for the third season of Enterprise and the latest issue of TV Guide has a preview. The article reveals plot twists for the May 21 season ender, "The Expanse," which has (spoiler warning!) a mysterious probe blasting a swath of destruction across North and Central America. As the article reveals, this is a preemptive strike by the Xindi (Zin-dee), an alien race that has obtained knowledge that Earth will destroy their homeworld 400 years in the future.

"We are about to do a first for Star Trek," Enterprise executive producer Rick Berman says in the magazine. "In the past, our captains have had the general mission to explore outer space and, in the case of Voyager, a mission to find a way back home. But there has never been a Trek series built around a specific mission and specific stakes — in this case, the very future of mankind." The TV Guide feature also reveals that Enterprise NX-01 will be retrofitted for war and we will see the use of photon torpedoes for the first time in Starfleet history. The ship will then be sent to the Delphic Expanse, a creepy Bermuda Triangle-type zone. Those who have entered this region before somehow become anatomically inverted, with skin on the inside and organs on the outside. "We find out that the Xindi space probe was merely a test and that they are creating an even more powerful weapon," Berman told TV Guide. "It's up to Captain Archer to go there and stop them from destroying us altogether."

The issue also offers a look at where the new storyline is headed, and what it means for some of the characters. T'Pol (Jolene Blalock), for example, is forced to resign from the Vulcan High Command and will appear in a new hairdo and catsuit.

The new issue of TV Guide (with Smallville stars Tom Welling and Kristin Kreuk on the cover) hits newsstands Monday, May 5.

What do you think of the upcoming changes? Discuss it at the Star Trek message boards!