The new episode of Fringe on Thursday night at 9 p.m. promises to be a pivotal outing in this sensational if (criminally!) under-watched season, electric with ideas and emotion. When we last saw Peter Bishop (Joshua Jackson), he had just been tipped off that the Olivia Dunham (Anna Torv) he’s been swapping spit with isn’t exactly the Olivia Dunham he thinks she is. Meanwhile, in the “over there” parallel world, “over here” Olivia, now operating with awareness of her true self, was busted by “Walternate” (John Noble), who now knows that she knows who she really is.