'Fringe' spoilers: Flash forward to the year 2609 in 'The Boy Must Live' -- plus, who will be sacrificed?

fringe-september-donald.jpgWe're still not ready to say goodbye to "Fringe," but we're going to have to get used to the idea -- there's only one more episode left before the two-hour finale event airs on January 18. Zap2it just got a sneak peek at the next new episode, "The Boy Must Live," which will air on January 11.

In the most recent episode, we barely had time to recover from Nina's death when it was revealed that Donald, Walter's mysterious partner in his quest to save the world, was actually September, our favorite Observer. In "The Boy Must Live," some of the biggest questions about September are finally answered when we reunite with the one who started it all.

The episode is best described as a gift to longtime fans of the show, returning to the core themes of the first season and packed with callbacks to memorable early moments, of both the heartwarming and heartbreaking variety. While we've been sworn to secrecy on some of the big twists, we can tell you six things to expect as we approach the series finale of one of the most underrated shows on television.

1. Olivia gets an eyeful. In the first of many callbacks to the pilot episode, Walter goes into the sensory deprivation tank to pull memories of September from his subconscious. He's not a fan of the swim trunks he's supposed to be wearing, though. "They were too restrictive. My body needs to be as free and open as my mind is so I can find September," he tells Olivia. It's good to know that even with his brain intact, Walter is still Walter.

2. Time travel to 2609. Captain Windmark blips into the distant future to get some answers -- and he admits that he's become consumed by the idea of eliminating Walter, Peter, and Olivia from existence entirely.

3. Walter and Peter's relationship shifts. We've always been a little bummed that in this timeline, Walter doesn't remember all of the development and growth that occurred between him and Peter over the course of the first three seasons. The father/son bonding was such an important theme to the show, so it was disappointing to have it erased, at least where Walter was concerned. There's some much-needed resolution to that in the very beginning of this episode. (We'll just say that we started crying less than three minutes in. We're not proud.)

4. The Observer origin story. We'll finally learn how they were created, and why. One particularly interesting piece of information? Because Observers don't feel romantic love, human methods of reproduction -- sex, y'all -- became inconvenient, and they developed a new way to reproduce, using genetic material from donors. Michael's genetic makeup is important.

5. A tiny spark of hope. As revealed in the above trailer for the episode, September and Walter's plan involves resetting time -- which gives Olivia hope that she and Peter may see Etta again. But we've seen in the past that wishful thinking can be a dangerous thing, and Peter is hesitant to be even cautiously optimistic.

6. One last sacrifice. This season, Etta and Nina both sacrificed their own lives for the greater good, making conscious decisions to die so that Walter, Peter, and Olivia could go on to save the world. In "The Boy Must Live," we learn that one more character we've grown to love will have to sacrifice his or her life in order to complete the plan.

Tune in January 11 at 9 p.m. EST.
Photo/Video credit: FOX