Nets are asking a lot of auds to devour a slew of new, complicated dramas

The broadcast nets are counting on an almost insatiable viewer appetite for serial this fall.

They’re serving up heaping doses of dramas and even comedies that boast ongoing storylines and sudsy touches that force audiences to make an appointment to watch each week. But will viewers save room for such a jam-packed menu?

Shows such as “Six Degrees,” “The Nine,” “Kidnapped,” “Heroes” and “Vanished” contain ongoing plotlines and mysteries in the vein of “Lost,” “Desperate Housewives” and “24.”

Some are sudsier, like ABC’s “Brothers & Sisters,” while others attempt to straddle the line between serialized elements and closed-ended stories (the CW’s “Runaway”). But they all boast story arcs that reward week-in/week-out loyalty — and will likely confuse the ones who check in sporadically.

“The old conventional wisdom of TV was, ‘Get ‘em in, get ‘em out,” says “Kidnapped” creator Jason Smilovic. “Now you want to keep them in — cliffhangers, twists and turns — in order to compel people to tune in.”

After years of network execs chasing after procedural dramas such as “Law & Order” and “CSI,” the pendulum swing was perhaps inevitable. While closed-ended shows perform well in the ratings and repeat strongly, they don’t inspire the kind of buzz that fuels magazine covers, iTunes downloads or rabid fan loyalty.

ABC Entertainment prexy Steve McPherson notes that the sheer glut of procedurals on the air makes it harder to add to the pot.

“We tried to develop some really closed-ended procedurals, and that’s a tough assignment right now,” he says. “There are a lot of good ones on. They’ve been played out with the franchising of ‘Law & Order’ and ‘CSI’ across the board, where you have 21 of those episodes airing a week.”

On the other hand, shows such as “Lost” and “24” do cultivate a cultlike fan devotion — and the success of those skeins, which aim to surprise and tantalize viewers (rather than comfort; think “Law & Order”) wasn’t lost on anyone in the business.

CBS Entertainment prexy Nina Tassler notes that critics just last year were wringing their hands over the glut of procedurals; this year, they’re up in arms over the perceived glut in serials.

“Obviously, with the success of certain serialized shows, there is a willingness on our part to embrace it and go with it,” she says.

It’s an age-old rule in TV: Hit serialized dramas beget more serialized dramas, just as smash reality skeins trigger more reality on the sked, and in the late ’90s popular comedies about young singles in Manhattan forced a glut of more comedies about twentysomethings living in the city.

“You have a lot of writing talent and studio talent that’s out there pursuing network spots,” McPherson notes. “And because of that, if there are things that are working, you get a lot in that area pitched to you.”

Josh Goldsmith and Cathy Yuspa, whose half-hour comedy “Big Day” will bow in midseason, say they came up with their show’s concept — a wedding day that unfolds over a seasonlong 22 episodes — partly because they knew the nets were looking for shows that can be promoted as events each week.

“We started thinking about how TV saves events for sweeps, like the wedding,” Goldsmith says. “Our thought was, can every episode be the big event? We started backing our way into the serialized, one-day idea.”

ABC’s fall sked is chock-a-block with serialized shows, which McPherson admits “present some challenges.”

For starters, serialized dramas rarely repeat well. In many cases, the networks are giving up on repeating serials altogether, even though its those second runs that generally make money for the webs.

“The performance of ’24’ (this summer) is somewhat near what we’re seeing on ‘Grey’s,’ ‘Desperate Housewives’ and ‘Lost,'” says Fox Entertainment prexy Peter Liguori. “It is very difficult to repeat a serialized show. I think part of that speaks to the power of appointment viewing of the originals.”

There’s also frequently a barrier to entry for new viewers, who feel like they can’t jump into a serialized show midway, lest they be helplessly lost inside the show’s plot. That indeed can be the case on shows with hefty backstories and mythology (“Lost” and “24”).

McPherson says it’s up to the net’s marketing team to make sure viewers aren’t intimidated by the fact that they’ve missed a few episodes.

“You’ve got to make sure you sustain and have an idea that people understand they can join the experience along the way,” he says.

“Runaway” exec producer Darren Star says he’s conscious of that.

“We’re not banking on people watching every episode,” he says. “There’s enough there that you could come in at any point and get the show.”

Then there’s the problem that has particularly rubbed TV critics the wrong way: What happens when a serialized show is prematurely canceled, and its few but loyal viewers are deprived of proper closure?

“As an industry on the whole, I think we all have to start thinking about that,” Liguori says. “If some of these serialized shows are canceled and there’s no explanation, no satisfaction, I’d have fear for next year when a bunch of serialized shows come out. Will audiences now be really gun-shy about committing to these shows?”

NBC Entertainment prexy Kevin Reilly says he takes that problem “seriously, particularly in this day and age of competition.

“We don’t like pissing off the customers,” he says. “And by the way, I get the emails. I wake up in the morning and I get, ‘Dear Moron.'”

Liguori says the nets should consult with show producers and studios to put plans in place in case a show doesn’t make it to the end.

One way, he says, is simple: Produce a final episode that wraps up loose ends. But that’s sometimes impossible, particularly for complicated shows that need more time to explain their mythology. More probable, Liguori thinks showrunners should explain online how the show would have ended.

Then, of course, there’s the question of just how many serials — with their weekly time commitment — viewers can sustain.

“People are only going to make an appointment and a commitment to a certain amount on the air,” McPherson says.

Adds Liguori, who notes both major trends to hit the primetime skeds this fall: “I think the whole industry is going to learn a lot about both serialized shows and single-camera comedies.”

Tassler, however, says she’s less concerned, and she warns against spending too much time worrying about whether viewers will accept more serialized shows.

“I don’t think the average audience sits at home and says, ‘Gee, this is a closed-ended episode. I’ll watch this,’ versus, ‘Oh, this is a serialized show. I’m going to watch that.’ It doesn’t happen that way. You watch a program because it’s good.”

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