About that story line. . .

Matt and Danny may be pulling good ratings with their fictional TV show, but NBC’s real-life numbers for “Studio 60 on the Sunset Strip” are another story.

Matthew Perry and Bradley Whitford star as a bickering writing duo on “Studio 60,” a show that presumes to rescue a once-funny late-night comedy show a la “Saturday Night Live.” But it’s become clear that writer Aaron Sorkin’s backstage drama needs a lifeline of its own. On Monday the show slipped to its lowest rating so far in the critical bracket of adults aged 18 to 49, with a 3.1 rating/8 share (7.8 million total viewers), according to early data from Nielsen Media Research.

“Studio 60” dragged down NBC’s performance for the night, although the network still narrowly beat CBS in the 18-to-49 demographic (4.7 average rating versus 4.5). The fantasy thriller “Heroes” has turned into a solid hit for NBC, this week handily winning the 9 p.m. time slot with a healthy 5.7 rating/13 share (13.1 million total viewers).

But “Studio 60” retained just 54% of that audience -- an anemic figure by any yardstick and especially for an expensive, heavily promoted show once considered NBC’s ace in the hole this season. Worst of all, “Studio 60” was beaten in both the demographic and among total viewers by ABC’s drama “What About Brian?” (3.5 rating/9 share; 8.3 million total viewers), a sluggish holdover from last season. CBS’ forensics fest “CSI: Miami” as usual dominated the 10 p.m. slot, with a 5.6 rating/14 share and 17.6 million viewers.

NBC is rightly touting its improved ratings performance this year. It’s the only network posting a year-to-year increase (up 15%) in the 18-to-49 demographic through the first four weeks of the season. However, all of that gain is attributable to NBC’s high-rated Sunday night NFL games. When Sunday nights this season and last are taken out of consideration, the network is flat in 18-to-49, with a 3.5 rating. That means that NBC’s entertainment programming is, taken as a whole, failing to find traction so far.

Channel Island is a blog about the television industry. For the latest posting, go to latimes.com/channelisland. Contact reporter Scott Collins at channelisland@latimes.com