"The L Word" premieres its final season Sunday, but it may not be the end of the road for the entire cast, as Showtime tells ET that a spinoff pilot has been shot that is "a substantially different show," according to the cable network's entertainment president Robert Greenblatt.

"We have been mysterious about the concept," continues Greenblatt. "One of the characters from 'The L Word' actually goes to prison. The show then goes to prison with a largely new cast. I would say it is not only lesbian characters; it is a big group of characters."

Although the "women in prison" genre in film and on television has been known for its campy value, the new show promises "a grittier look; it is not as dark as 'Oz.'"

Greenblatt adds that the spinoff is anchored by Leisha Hailey, who plays bisexual NPR journalist Alice Pieszecki on "The L Word," and there are three guest stars in the pilot: Melissa Leo, Famke Janssen and Laurie Metcalf.

"Whether they continue in the series, we don't know yet," says Greenblatt.