Thursday night could be the culmination of one of the biggest risks a network television series has taken, creatively, in years.

The two-hour finale of "Lost" essentially remakes the show, offering bold new challenges. And it's a template that other aging series should consider. After all, who wants the same old thing week after week?

Here's how "Lost" transformed itself from an overly complicated drama that was imploding from its own plodding mythology to a nimble and daring "new" drama: It announced its own sell-by date.

The trouble with serialized dramas - meaning shows that are not self-contained in the hour, but have a continuing, often complicated, story line - is that even when the producers and
writers think they know how it all ends, they're wrong.

When "Lost" started, creator J.J. Abrams said there was a five-year plan. It's what networks want to hear. Yes, you know how it all ends, how the mysteries unravel and how everything will be explained to our loyal audience. It's a good pitch, and it might even have been true at the time. But writers invent things. That's what they
do. Twists. New characters. Changing behaviors. And sometimes the narrative thread just escapes them.