Looks like NBC's Day One will have more in common with ABC's upcoming V than with CBS' lamented Jericho in the post-apocalyptic drama derby. (Massive spoilers ahead!)

NBC President of Prime Time Entertainment Angela Bromstad spilled more details about the show in a group interview following her press conference today in Pasadena, Calif., as part of the Television Critics Association's summer press tour, and she gave up a big piece of the show's premise: It's about an aliens.

"It's an alien invasion," Bromstad said. "Not just a disaster. It's an alien invasion." That appears to confirm impressions left by a grainy trailer for the show that was leaked online.

Earlier, Bromstad had said the show might be of limited duration and tell a contained story, but she declined to be more specific about how many episodes that first, and possibly only, season will contain.

"We're still determining that," Bromstad said. "We're getting scripts in next week. We have three additional scripts coming in, so we're still talking to [series creator] Jesse [Alexander] about what our programming needs are and creative needs."

Bromstad is encouraged by the amount of genre programming on other networks. "I think it's a very rich area now," she said. "Before Lost came on, there wasn't really that much out there before Lost and Heroes. Now we've got Lost, Heroes, FlashForward, V, in addition to great stuff on Syfy. It's just a really fertile, rich area to channel right now."

Meanwhile, Bromstad talked a bit about the returning series Chuck. Chuck fans may still have a long wait until that show returns midseason. Bromstad offered some hope that it may run earlier, or extend longer once it starts.

"The great thing with Chuck is that they're on a great track creatively," she said. "We've got three or four scripts in already, so it is something that we can move around, but right now it's not scheduled to come on until March. It's only got a 13-episode pickup. We have talked about 'Is Chuck something that we allow to run over into the summer and be part of our summer programming?' Those are just discussions that we're going to continue to have. Right now it's due to come on midseason."

Bromstad said she is confident the audience will return no matter when she decides to slot it on the schedule. "Chuck has a really loyal fan base, so we thought that that would help sustain it," Bromstad said. "I think that we were anxious to put on new shows. Because we're down to 8 to 10 o'clock, we really wanted to put as many new shows on as possible."

Fan campaigns helped contribute to Chuck's renewal, but they were not the only factor. "I think fans and critics were instrumental in keeping that show," Bromstad said. "We love the show. The ratings were instrumental in keeping that show."

NBC did let its genre mystery Medium go, and it moves to CBS in the fall. Bromstad said it was a tough call. "I love [producer] Glenn [Gordon Caron], I love that show," Bromstad said. "The intention was always to pick it up. We weren't able to make a deal. We were able to make a deal on Chuck. Chuck fits in our brand. We had to make those choices, and [Chuck]'s a little bit of a younger show as well."