Credit: Michael Yarish/CBS

It’s one of the biggest mysteries of the upfront season: What is CBS going to do with CSI?

The rumors have been flying these past couple weeks, with each twist keeping industry insiders guessing. All seem to agree that CBS will renew CSI. Likewise, rumors are consistent that the 16th round will be the final season, and a shorter-than-usual one, as well.

But on Friday, word along Wilshire Boulevard crystallized into a surprising twist: CBS is interested in potentially wrapping up one of the longest-running crime dramas with a two-hour TV movie (likely written by creators Anthony Zuiker and Ann Donahue). That’s just one scenario being considered, however. We also heard possibilities of a 13-episode final season, or four episodes and then a TV movie.

There is another factor that has not been previously reported, as well: We’re told CBS is hoping to persuade original CSI star William Petersen to return for the final two hours. There is no deal for this. As of now, it’s not happening. But we’re told CBS has long been interested in having Petersen—who starred in the show’s first nine season—return for the finale and that it’s something the network currently hopes to pull off in this final order.

In any case, if CSI does end next season, it will mark the end of an era. CSI ushered in a wave of gritty procedural crime dramas using technology-based murder-solving methods with an ensemble cast. The slick production and intriguing mysteries made the show a hit when it launched in 2000, and eventually spawned several spinoffs—CSI: Miami, CSI: New York and the recently launched CSI: Cyber (which, despite modest ratings, is looking good for a renewal as of now).

The flagship series helped give CBS its programming brand for the 21st century. The broadcaster’s other hit franchises like NCIS (a spinoff of the CSI-pre-dating JAG) and Criminal Minds flourished in CSI’s wake and collectively established CBS as a network for crime dramas, a format that’s proved a sturdy performer year after year while rivals chased flashier concepts. Moreover, while critics often mocked CBS spinning-off CSI—which made the creative art of storytelling look like managing a chain restaurant franchise—one can’t argue with the technique’s success, and now nearly every hit show with a procedural element is eyed for a spinoff.

More to come over the next several days as CBS—and all the other broadcasters—finalize their fall plans.