For five years, "Lost" has managed to surprise its viewers, its actors and its network bosses.

Now the biggest surprises may be ahead: Tonight, the show starts its final season.

The opener's script, said Jorge Garcia (who plays Hurley), "is definitely like: 'What? Wait! Let me read that part again. What!?' There are some head-scratchers."

Emilie de Raven (Claire) agreed. "I had to read it about three times before it actually made sense."

Then she added, as an after-thought: "In a great way."

The rap against "Lost" has always been its confusion. Viewers say they get ... well, lost.

One solution, said producer Carlton Cuse, is a special that airs tonight. It's "a summation of the five seasons in 43 minutes (plus commercials), which is actually pretty remarkably well-done."

At the beginning of the five-season journey so far: a plane crashing on a mysterious island. On the other, last season's finale: Jack felt a bomb would destroy the island and undo everything that had occurred.

"Juliet hits this bomb," Cuse said. "There's a white flash. What happened?"

The season starts in the moments after the flash, he said. Until then, viewers won't know what happened. They're used to that; so are the actors.

Last season, Terry O'Quinn was told obliquely that he should play John Locke a bit differently. Late in the season, he heard the rest: The real Locke is dead; he's been playing someone who looks like him. "It was easier to play whoever Locke is now, before I knew I wasn't playing Locke," he said.

This is not what actors are used to.

"Working on 'Lost' has upset most of my previous ideas about actor preparation," said Michael Emerson. "It's actually better (on 'Lost') groping around a bit. And it's nice not to be burdened with the secrets."

He was signed to play a few episodes as the leader of the Others, who were on the island before the crash. That evolved into his chilling portrayal of Ben Linus. "I have lots of fond memories of breathless confrontations in small rooms. ... Those kind of scenes are always so dark and scary."

Usually in control, Ben suddenly lashed out in the season-finale, killing the man (Jacob) who had been giving him orders. "The character I play behaves in a calculated way often enough," Emerson said. "Every once in a while, he does something completely childish or impulsive."

Other characters also make dizzying leaps. Josh Holloway recalls the early episodes, when Sawyer was just another tough guy.

"I read the pilot and I was like, 'This guy's such a (jerk). I gotta figure out how to stay alive,' " Holloway said. "I remember telling my wife, 'Don't throw away those boxes, because unless he's got another dimension, he's going to be killed quickly.' "

Dimensions were added, including warm romances. "I really thought the audience might reject that softer side of Sawyer," Holloway said.

It didn't. It even accepted Sawyer being an authority figure when the island time jumped back to 1977. "If you had said that was going to be his eventual path ... it would have sounded like the most ridiculous thing," said producer Damon Lindelof.

Any of these shifts would sound odd. Lindelof recalls walking with Cuse to the ABC offices, to explain plans for the next season. "Carlton and I (turned) to each other, going: 'Is there any other way to say time travel without saying time travel?' "

There isn't. "Lost" leaps in time; its season-opener may or may not take a mega-leap.

It's sort of epic, Holloway said. "It felt like a finale, that scale. Wow!"