By Piya Sinha-Roy

LOS ANGELES (Reuters) - "Fringe" fans may be feeling bittersweet as the sci-fi TV show enters its final season, but executive producer J.H. Wyman pledged on Wednesday to give fans a satisfying conclusion and "the love letter they deserve."

"Fringe," co-created by J.J. Abrams of "Lost" and "Alias" fame, Alex Kurtzman and Roberto Orci, follows a FBI team who use methods outside of mainstream science to solve mysteries relating to a parallel universe.

The fifth and final season, which starts on Friday on Fox, will pick up from the "Letters in Transit" episode in April 2011 that threw the series into year 2036, where the original Fringe team is freed from encasement in amber and must face a dystopian society.

Wyman, also a writer on "Fringe," told reporters in a conference call on Wednesday that he "fell in love" with setting the story in the future, and wanted to focus the final season on the show's characters.

Peter Bishop (played by Joshua Jackson) and Olivia Dunham (Anna Torv) provide the main love story of the series as their relationship struggles in the face of time-bending obstacles.

"No love story worth telling is an easy love story. It's the hills and the valleys that make a relationship, in my opinion, really dynamic and worth watching and the harder the tale, the more worthy the pay-off," Wyman said.

While he declined to reveal details of upcoming plots, Wyman said he hoped fans would "enjoy the surprises", and that the ending would satisfy audiences and give the fans "the love letter they deserve."

"I want to feel that my characters evolved in a place that they deserved, sometimes maybe unexpectedly, but logically they've come to a conclusion that makes me feel satisfied," Wyman said.

"I want to tell these real odyssey stories about these people, and give them a little more sense of continuity," he added.

"Fringe," which combines science fiction with elements of police procedural drama, debuted on Fox in 2008 averaging 10 million viewers in its first season. It became a cult favorite, but ratings slipped last season to about 4.2 million viewers.

(Reporting By Piya Sinha-Roy, editing by Jill Serjeant and David Gregorio)