REVIEW (spoilers from previous seasons):
Season 3 starts with showing us how FauxOlivia has taken the part of real Olivia to the real world and how Olivia trying to survive at the other universe. After some point, and a lot of events that happened, each Olivia goes back to her worlds. Walter and Bishop are working on Walternate's machine. The observers are the usual weirdos who don't make sense.
Season 3 was the only season, that only few of the episodes weren't part of the main story but simple individuals. I think i liked that. And there was also episodes and fringe division accident on both sides. Our universe had the usual blueish opening while the other universe has a redish opening. One episode which was in the future had a greyish opening. I really love all those small things they do! Also, the observers had bigger part in it and you get to know some answers to some of the questions. Just a few though, still they are the biggest question of Fringe.
It's my 2nd favorite season (season 2 was my best) because we see both sides, there are many things happening and you finally see the true potential of the actors. All of them (except Peter), had to play full episodes with of the same person but with different characters. It was nice to see how they did that, and how good it was. You could actually believe that FauxOlivia-Olivia and Walternate-Walter were two different persons! They managed to fill them with life and show us their history.
The end has both universes and the machine open, trying to destroy one another. I'm not telling you who wins but i'm telling the very last scene was a huge "WHAT THE FUCK?". They knew exactly what do to bring their viewers back for the next season.
Once again it's full of awesome guest stars, Walter making even more new names Astir (how is that even possible?), full of action, new creepy events and lots of fun.