The plot thickens

Madly in love with ''24," or ''Invasion," or ''Prison Break," or ''Family Guy"?

Then get ready to spend more, a lot more, time with it.

In the coming months, you and your TV addiction are going to be reeled into an expanded ''environment" of your favorite network show, one that may require a cover charge for entry into certain exclusive zones.

You'll be invited to visit characters' blogs at MySpace.com, or pay for mobile phone episodes (known as mobisodes), or buy DVD packages and video games containing new and additional plot information. Your once-simple affair with your TV ''story" could have as much to do with your PC, your cellphone, and your DVD player as it does with your TV set.

In other words, your relationship is starting to get complicated. Network TV is becoming only the first step in what is known as a ''TV series." It's becoming an entry point to show-o-spheres, where you not only watch ''24" on Mondays on Fox but you purchase a ''24" DVD set that contains clues to the season's big mysteries.

You not only watch ''Lost" on Wednesdays on ABC but you check into the weekly podcast to hear, say, Adewale Akinnuoye-Agbaje talk about playing Eko. You don't just laugh at ''The Office" on Tuesdays; you laugh at Dwight's blog entries on the NBC site and on MySpace. Recently, ''Invasion" even included a plot in which paranoid Dave was abducted because of his blog, which actually exists on ABC's site. And Neil Patrick Harris's Barney on ''How I Met Your Mother" frequently refers to his blog, which is on the CBS site.

Extras such as commentary and deleted scenes have been with us for years on DVDs, and of course T-shirts and knickknacks are Marketing 101. But now timely information and integral plot and character developments are also becoming available outside of the televised mothership. Last week, for example, Fox announced plans to create new episodes of its animated hit ''Family Guy" exclusively for the Web next year, for a fee.

''Audience viewing habits are evolving," says Nina Tassler, president of CBS Entertainment. ''And to that end, we want to be there with them when they want to view elements of their favorite TV shows." She says viewers are showing increasing loyalty and commitment to their top series, so that they're now more willing to explore beyond what comes to them free from the network.

''We're doing it in drama, comedy, and alternative," Tassler says about CBS's plans to expand on its shows. ''But right now a lot of the stuff is under the cone of silence in the development world."

Last week, the network did announce a deal with Verizon Wireless' V Cast multimedia service that will offer cellphone users previews and original behind-the-scenes material. The price for these snippets has yet to be announced, but in the past, mobisodes, including a series based on Fox's ''The Simple Life," have sold for 99 cents apiece.

Fox's ''24" has been a pioneer of these new content delivery methods. The growing fan loyalty that Tassler mentions is most obvious in a dramatic serial like ''24," as well as ''Lost," ''Invasion," and ''Prison Break." These shows succeed in getting mass audiences to scrutinize every detail on a weekly basis and to go to all ends -- including, now, their video-equipped iPods -- to stay up-to-date. They foster an Internet culture where guesswork, spoilers, and misinformation thrive, and they breed the kinds of viewers willing to pay to know all.

Increasingly, their audiences may divide into circles of knowledge -- old-schoolers who solely rely on the weekly ad-driven freebie; those who pursue free plot and character news in other media; and those who pursue with their wallets open.

''I'm personally very interested in this re-forming television model, that things are happening technologically that are changing . . . the way we consume our entertainment," says Howard Gordon, one of the ''24" executive producers. ''And '24' is particularly right for [experimentation] both in terms of its serialized nature but also because it is a high-tech kind of show, so that the gadgetry and the feeling of it lends itself to things like mobisodes and [video] games."

The new season four DVD set of ''24" offers a prequel to season five that will not air on TV, even while it illuminates Jack Bauer's story line. (Season five premieres with a two-hour special on Jan. 15.) The short, about 12 minutes long, gives us Kiefer Sutherland's Bauer in a scruffy mullet a year after season four ended and a few months before season five will begin. Skulking around Chicago, supposedly dead, he secretly meets with former CTU colleague Chloe and gets chased by a BMW. You may have been obsessed with ''24" for four seasons, and plan to stay glued to the fifth, but you don't fully know Jack unless you've got the DVDs.

A new ''24" Playstation 2 product, ''24: The Game," will also include exclusive plot information, although in this case the action is set during the interim between seasons two and three. Due in stores on Feb. 28, the game will explain how President Palmer recovered from the attempt on his life, how Jack got involved with the Salazar drug ring, and how Chase came to CTU. This new plot material will be mostly unimportant to those who've kept up with the series; but it may matter to those just now catching up with the show on DVD. Unlike fan fiction, which finds loyal watchers posting their own TV show-related stories online, the game material will be officially authorized.

The makers of ''24" have also put together a series of 24 mobisodes that last a minute apiece and follow a ''24"-like adventure in counterterrorism. The mobisodes, also now available on the season four DVD, take place in Washington, D.C., while the TV series is set in LA. And they only include actors not seen on TV's ''24" -- something that won't change until a business model is developed with acting and writing unions in mind. Producers still haven't determined what fee a TV show's actors and writers would make for participating in mobile material, especially since mobisodes are so new to the market.

''We were very, very specific that the mobisodes had nothing to do with the series," Gordon says, ''except as a feeling, and as a marketing tool more than anything else." But the mobisodes do contain references to the TV plot, with lines such as ''We think this is tied into what happened to Secretary of Defense Heller in Los Angeles this morning."

Are TV viewers about to feel betrayed by their shows? Will their direct and intimate relationship to the narratives of ''24" and ''Family Guy" be tested in the coming years? Mobisodes are in their early stages, both technologically and in terms of public awareness; TV viewers have only recently gotten used to the idea of text voting for reality shows. According to Linda Barrabee, an analyst at the Yankee Group research firm in Boston, ''It's still pretty early in the adoption of these kinds of service on a phone." Of the 194 million cell subscribers in the country, she says, ''under a million are actually watching video on a phone."

But still, the format could evolve into something significantly more than a novelty, Barrabee says, particularly as users can get news and sports on their phones: ''That's what resonates first." She says networks can easily see the great potential of mobile video, since two-thirds of the market already has cellphones and because phones are such personalized items. ''My phone is about me," Barrabee says of our relationships with our cellphones, ''so I should be able to get what I want on my phone."

CBS's Tassler says the network is sensitive to viewers who don't choose to explore their TV shows beyond TV. ''At the same time, we want to make sure that those members of our audience who want to watch more and more content feel satisfied as well, and that we continue to provide them with a fulfilling viewing experience. If there are additional elements online, if there are additional elements on a mobisode, they all have to complement each other but at the same time they have to be stand-alone."

Gordon of ''24" says he is careful not to ''blackmail" the viewer. In his opinion, he says, ''the DVD prequel was never really anything anyone had to hunt down and see to enjoy or understand the season."

''People who go to the trouble of spending money on a DVD are entitled to something more than what everybody got the first time around," he explains. ''So I have no objection in principle to the idea of having something that's exclusive to the DVD. But I think we are very mindful of not leveraging the people who are entitled to see the show for free, of course -- as long as they watch the commercials.

''But the show should stand on its own. That's where all our efforts are. We never do anything that's going to take away from the show."

Matthew Gilbert can be reached at gilbert@globe.com.