Save the cheerleader, save the world? Or merely save the network? NBC has enjoyed the success of “Heroes” (8 p.m., NBC), one of the bona-fide hits to emerge from the past TV season and one of the bright spots for the beleaguered Peacock network.

The first season of “Heroes” concludes tonight with as crowded a cast and as complicated a story arc as one can possibly follow on a TV drama. To begin to explain this comic-book prophecy of a nuclear explosion in New York, and a cockeyed caravan of gifted mutants with special abilities and baffling motivations, is beyond the scope of a mere TV column.

The series seems to be an organic outgrowth of NBC-Universal’s strength in science-fiction storytelling. “Battlestar Galactica” tops many viewers’ lists as one of the best dramas on any outlet – cable or network. And it often struck me that the series “Eureka” and “The 4400” (on USA) were stronger dramas than some on network television.

The distinctions between cable and network have become more porous. Last week, NBC announced that starting next season, it will move “Law & Order: Criminal Intent” to USA but would reserve the right to air repeats of the show on NBC. The season finale airs tonight (9 p.m., NBC).

¢ When I look back at this season of “24” (7 p.m., Fox), concluding tonight with a two-hour finale, I’m reminded of last year’s “American Idol” signature sing-off: “So you’ve had a bad day …”

This has been a bad day for Jack Bauer and a bad year for “24,” but there’s no reason things can’t improve. Fox, as if channeling Scarlett O’Hara, assures everyone that “tomorrow is another day” and has renewed the series for two more seasons.

One way to improve “24” is to regain the audience’s respect. When the fate of the world is at stake, not every crisis has to be driven by personal connection. Here we are in the 23rd and 24th hour, and it’s hard to tell whether Jack is trying to avert war with Russia or just save his nephew and confront his father.

This emotionally claustrophobic theme has run throughout the season. The head of CTU is married to the national-security adviser; the vice president’s lover is sleeping with a Russian spy; the only guy who can infiltrate a prison is the lover of the president’s sister, and the only way to reach the premier of Russia is with a phone call to his wife from the iffy former first lady. (Hey, is Logan dead or what?) It reminds me of “Dallas” when all of those billionaires had to live in the same house.

And I’ve missed Chloe’s emotionally stunted personality and socially awkward outbursts. At her best, she’s always seemed like someone from “The Office” who wandered into CTU. She just hasn’t been the same since she was saddled with a significant other. Let Chloe be Chloe!

Tonight’s other highlights

¢ The competition continues on “Dancing with the Stars” (7 p.m., ABC).

¢ “Cities of the Underworld” (8 p.m., History) explores the caves of Budapest.

¢ The countdown continues on “50 Most Shocking Celebrity Scandals” (8 p.m., E!).

¢ Two ladies in search of one ring on “The Bachelor” (9 p.m., ABC).