When ABC's drama “;Lost”; ends in May, it will definitively end. Don't look for any sequels or spinoffs.

The show's producers said they've known the final image of the mythologically dense series about Oceanic Airlines Flight 815 since the first season, although Carlton Cuse said the last episode hasn't been written yet. It will air in May.

Cuse and Damon Lindelof are giving away few secrets but can say the sixth and final season will hark back to its first and most popular season in 2004.

The two-hour season opener tonight promises to be a challenging episode. Actress Emilie de Ravin said she had to read the script three times before it made any sense. “;Get ready to scratch your heads, America,”; Lindelof said.

In its lifetime, “;Lost”; proved that it's possible for a television series to challenge its viewers and pull off production values that rival feature films, said Stephen McPherson, ABC entertainment president.

One secret producers did reveal is that actress Cynthia Watros, who played the character Libby before being killed off in the second season, will return this year.

“;Finally, all of your questions (about Libby) will be answered,”; Cuse said.

“;No, they will not,”; Lindelof said.

Fans should prepare themselves in that not all of the questions raised during the series will be answered. “;That would be too pedantic,”; Cuse said.

They're hoping that final show is something that will be talked about afterward in much the same way as the diner scene that ended “;The Sopranos.”;

“;I don't think it would be 'Lost' if there wasn't any arguing and active debate among the viewers about whether or not it was a good ending,”; Lindelof said. “;My mom will say it's a good ending, even though she doesn't understand the show.”;

Actors said filming the series has been an emotional journey.

“;I'm going to cry like a baby when this series ends,”; actress Evangeline Lilly said.