Some of these questions may yield reasonable answers with just a bit of fan-tweaking. Peter was an anomaly anyway, having popped back into existence for no reason at all early in season four, so presumably anything relating to him and his presence Over Here – and the creation of the door that Walter wouldn’t have otherwise needed to create, sparking off the whole series – is just a bit, for want of a better phrase, wibbly-wobbly-timey-wimey. Amy Jessup obviously found better things to do and there were brief handwaves in season four to get rid of Rachel and Ella and Scarlie. The mysterious criminals who were after Peter disappeared so long ago everyone’s probably forgotten about them, and as of season four Peter never existed for them anyway. But some things will remain eternally a mystery – there’s just no explanation for Nina and Broyles.

Perhaps the real question is, should the finale have answered all our questions? Is it the job of a series finale to wrap everything up in a neat little bow? As io9 has pointed out, Fringe was always more about family, and parent/child relationships in particular, than it was about weird science (this had been obvious from at least season two – just count how many season two episodes are about parents going to extreme lengths for their children. Or, in one case, performing dangerous scientific experiments on their children). If we didn’t already know that emotional truth was more important to the show than scientific accuracy, Peter’s utterly nonsensical existence in season two, and Olivia’s equally nonsensical recovery of her memories of him, was a dead giveaway. So why might we expect more from the series finale?

Perhaps Fringe’s problem is that, when it comes to long-term storytelling and payoff, it set the bar too high too early on. Season two’s Peter is one of the most satisfying revelation-episodes in a long term story arc that you’re ever likely to see. At that point in the series (before season three’s Subject 13, which is one big continuity hole), Peter offers an explanation for slow-burning plots that ties in to the tiniest hints dropped throughout seasons one and two (Peter thought GI Joe’s scar was on the other side of his face, he’s always hated custard even though Walter insists he enjoyed it as a child) as well as explaining most of the bigger mysteries that the show had been pursuing up to that point – not only why Peter has a gravestone and Walter remembers his death and a partial explanation for why September saved them from drowning in Reiden Lake, but also an explanation for the Pattern and for why Fringe events have been happening at all. And the explanation itself is a doozy: Walter caused all these Fringe events, causing thousands of deaths in our universe and probably millions Over There, because he was desperate to save a single life, that of his son. It’s a beautiful and yet chilling metaphor for the abuse of science, but more importantly for the lengths to which a parent will go to save their child. In Peter, the logic of the science fiction and emotion come together to create an almost perfect arc-based episode.

So maybe that’s why we might have expected more from the Fringe finale. We’d all like to recreate the experience of watching Peter for the first time and being impressed by a story arc that had been so carefully thought out and that came together so beautifully. But TV writers and producers can only do so much intricate long-term planning and after five years, it’s probably not possible to tie all the loose ends up so neatly (not to mention the host of anomalies created by season four).

But that one, big unanswered question – why did the timeline snap back into place in 2015 when the Observers had had such a huge impact on events before that date? – will still bother some viewers. Ultimately, it comes down to how far you are willing to suspend disbelief in terms of science fiction for the sake of emotional truth. Because (Nina and Broyles’ alternate timeline hijinks aside) Fringe’s emotional stories were wrapped up perfectly in this finale. Olivia gets the chance to be a mother, Walter shows Astrid how much she means to him, Broyles kicks ass and a few episodes earlier, Nina proved her true mettle when she killed herself to protect our heroes. And the most important of all, those last words Peter mouthed to Walter as he stepped through the portal – “I love you, Dad.” From their frosty reunion in the pilot, through the shattering revelations of the end of season two, to putting Peter on the opposite foot in season four when suddenly he had to pursue Walter’s love instead of vice versa, Fringe’s five-year story has been about Walter’s love for his son and, eventually, his son’s for him. For some, that won’t be enough, for a story that doesn’t make logical sense will remain forever naggingly unsatisfying. For others, that swell of emotion renders all logical inconsistencies null and void. Both points of view are equally valid: both will be as strongly felt.