The story for the final season of Fringe is already in place.  Walter (or at least the Walter of 20-something years ago) has recorded a series of tapes that will explain how to stop the observers (or the invaders) and their plans for total domination of Earth.  So at least the first half of the season will likely be taken up by the team’s search for these tapes, and thanks to the magic of Walter Bishop’s character, they are not easy to find, nor are the things they need to make Walter’s plans a reality.

Astrid uses the laser to melt amber around what they believe is the first tape.  After she successfully removes it without any damage (although Walter tells Olivia that he has just retrieved it himself), they play it, only to discover that it’s actually tape number 3.  But the tape tells them that they need to head to Pennsylvania where they will find a crucial element of the plan.

When they reach their destination, they encounter a group of people with strange markings on their faces and bodies.  A man named Edwin appears to be the group’s leader, and he recognises Walter, although Walter doesn’t recognise him.  It seems that Fringe division has a cult following in the future, with Edwin’s young son presenting Olivia, Peter and Etta with copies of Fringe comic books, that he wants them to sign.  The group have taken up the task of trying to record history as it happens, in an effort to stop the observers from re-writing it as they see fit.  So they have data cubes they are able to search through, although none match up with what the team is looking for.

Astrid has remained at the laboratory to try and restore the tape to understand a part of it that was previously warped and undecipherable.  She eventually clears the picture up enough to hear Walter mention a mine in the area, and Edwin remembers that the observers once took a man who had entered the mine captive.  Walter believes he was taken as he was attempting to manufacture a suit that would allow people to enter the mine and get a hold of the minerals inside it.  He discovers that the atmosphere has changed in this part of Pennsylvania, and the atmosphere inside the mine calcifies humans at an accelerated rate, which explains the strange markings on the bodies of those that live there.  When Olivia and Walter start to show signs of the same symptoms, they realise they are running out of time to get what they need.  Their need is further accelerated when members of the resistance warn Etta that the observers know where they are and have sent troops to capture them.

Edwin makes contact with another group who live nearer the mine, in an attempt to bargain with them and allow the team to go into the mine.  But he later tells them that he can’t go with them, seemingly afraid of the impending arrival of the observer’s troops and the effects of the mine.  But he’s actually sent them away from the mine, and when they discover this, they go to the real entrance of the mine and find a bucket filled with the mineral.  Edwin has sacrificed himself to get them what they need, and they are able to escape before the observer’s men arrive.

It’s not the best episode of the season so far, but it is an episode of the kind Fringe has always done well.  There’s the weird science of the atmospheric effects on the people living in the camp, and characters that aren’t likely to re-appear in future episodes are given key roles.  So the search for the tapes and all the missing pieces that will help the team rid the world of the observers continues, and the final season continues to be tightly written and focussed.