Things go from bad to worse to much, much worse in this week's "Falling Skies" (Sundays at 9 p.m. ET on TNT), which is a gripping hour of television.

In this exclusive clip, Anne (Moon Bloodgood) and Lourdes (Seychelle Gabriel) are in the basement of the hospital, attempting to help Jamil, Lourdes' wounded boyfriend. One of many signs that things aren't going very well? Their security detail is Matt (Maxim Knight), the youngest son of Tom Mason (Noah Wyle). The show's willingness to put all of its characters in realistic danger is one of the best things about the second season of "Falling Skies," which improves quite a bit on its first.

The women barely have time to assess Jamil's condition when Matt points out another problem: There are sounds coming from (and holes appearing in) a door near the trio. What could that mean? Given that this is "Falling Skies," and everyone on screen recently survived an apocalyptic alien invasion, you're right -- it means another very bad thing is about to happen.

What makes Sunday's episode outstanding is that the problems in the basement are far from the only challenges confronting the survivors holed up at the hospital. It would be churlish to give away what's going on upstairs, but viewers saw at the end of the last episode that Ben decided to run off with Karen, his fellow harnessee. Let's just say there are complications on that front, and the situation for Tom, Captain Weaver and the rest of the survivors becomes intense very quickly.

Sunday's episode is an action-packed hour that doesn't just revel in its crisp pace; the actions and choices of the core characters reveal quite a bit about them. In fact, Sunday's taut episode is one of the most tense -- and enjoyable -- hours of "Falling Skies" yet.

It is, among other things, proof that TNT made the right call to renew this much-improved drama for a third season.