BEVERLY HILLS, Calif. — Fox's new series "Reunion" is nothing if not ambitious.

It's not the first show to revolve around a murder mystery that takes an entire season to unravel. But it is the first to spread that mystery out over two decades.

"Reunion" (Thursday, 8 p.m., Fox/Ch. 13) takes us through two decades in the lives of six friends we meet in the summer of 1986, just after they've graduated from high school.

Will (Will Estes) can't wait to start his college career — he's got an athletic scholarship. But his loyalty to rich, spoiled Craig (Sean Faris) might put that in danger. Craig, meanwhile, isn't aware that his girlfriend, Samantha (Alexa Davalos) is hiding a secret.

Jenna (Amanda Righetti) has big dreams and bad judgment. And she has never caught on to the fact that Aaron (Dave Annable) is in love with her.

And there's sweet and innocent Carla (Chyler Leigh), who has changed — a lot — by the time five of the six reunite at the present-day funeral of the sixth.

"We feel like there's two mysteries — who's dead and who killed them," Feldman said. The first answer will be revealed "not too far into the season."

"After that, the gloves are off and . . . we track all the clues, all the motives, all the suspects, building toward a revelation of who the murderer is" in the season finale.

Along the way, each episode will take place in a succeeding year — Episode 2 in 1987, Episode 3 in 1988, and so on. (The plan is for two two-part episodes, which would bring the total to 22.)

"The goal is to have episodes in which you have self-contained elements but also reward your regular viewers with things that do pay off over the course of the season," Feldman said. "You want to lay in clues in episode one that maybe can help you solve the mystery in episode 22. But at the same time, you want to tell stories that are as self-contained as possible in each year."

Of course, as it will be for Det. Marjorino (Mathew St. Patrick of "Six Feet Under"), it won't be easy to get at the truth.

"They have secrets. They have something to hide, so I wouldn't take everything they say at face value," Feldman said.

The ride may be a bit bumpy, but — if the pilot episode is any indication — it looks like once you get on this ride you won't want to get off.

AS IS THE NORM for new series, only 13 episodes of "Reunion" have been ordered by Fox. Feldman is, of course, hoping to get a "back nine" order to complete his murder mystery. But if not . . . "Will I tie it up? Absolutely," he said.