Spoiler alert: this piece is all spoilers. It will also read as nonsense if you aren’t already familiar with words like “Quaffle.”

It’s fair to say — and it’s been said, a lot — that Harry Potter and the Cursed Child‘s vision of time travel brings it into dangerous territory of inconsistency with the books, as far as seeing it as “canon” goes. If one decides to consider the script (conceived by Rowling, Jack Thorne and John Tiffany, and written by Thorne) as anything more than elaborate fan-fiction, it risks undermining arguably one of the coolest sequences throughout any of the books — the double-climax of Harry Potter and the Prisoner of Azkaban, in which past-Harry Potter unknowingly experiences the doings of future-Harry Potter, and future-Harry Potter then unknowingly goes back in time to fulfill a past that’s already been predetermined. (Yes, when time travel is involved, all sentences sound this convoluted.) That initial vision of HP universe time travel — and incidental animal rights activism, what with that radical Hippogriff rescue — hinged on the predestination paradox. And given its existence within a book about a prophecy, that narrative choice made thematic sense.

Asking whether something contradicts canon doesn’t really demand much beyond a “yes” or a “no” answer — and the answer pretty clearly here is “yes,” regardless of how much the discrepancy between book and play may be cursorily justified through an “if you go back more than a few hours, everything gets fucked up” rule. It’s easy to see where fantastic direction and a visionary design team could make something moving out of Cursed Child, but on paper its opening of multiple alternate universes dulls the importance of the iconized journey we went on across thousands of pages of Rowling’s writing, in her one vivid, robust, specific universe. The fragmentation in the play makes the story we’ve followed so closely seem flimsy.

Artistic quibbles aside, the philosophical question that remains is more interesting. Which theory of time travel — books or play — fits better within the world we’ve come to know and love? Again, Rowling’s original vision fits more seamlessly into her epic: the second part of Prisoner of Azkaban’s climax is about sticking to what’s already been written — not changing the past, but having always been that past. Cursed Child is all about rewriting the past — it exists within a world where all you need to do to decimate seven books’ worth of a battle between a boy and a hissing supervillain is go back in time and embarrass a hot dude— as Harry Potter and Draco Malfoy’s sons somewhat accidentally do — and let the butterfly effect do the rest of the work. (That hot dude, Cedric Diggory, in turn becomes a Death Eater, kills Neville Longbottom, and prevents the overthrow of Voldemort from ever coming to pass.)

Still from Chris Marker’s ‘La Jetée’

While the kids in the Cursed Child are all too able to change the past and thereby create drastically different futures than the ones they’ve already lived, that was not the mode of time travel in HP3. Azkaban‘s instance of backwards causation in time travel became an impressive narrative device familiar to anyone who’d seen one of the most elegant narrative portraits of time travel: Chris Marker’s La Jetée (or, of course, Terry Gilliam’s adaptation, 12 Monkeys). While Marker’s 28-minute film-in-photographs revealed that a character was bound by the predestination paradox to witness his own death, Prisoner of Azkaban uses a similar formula of temporal predestination to bring about a character’s evolution. The Stanford Encyclopedia of Philosophy describes the type of time travel depicted in Rowling’s third Harry Potter novel:

[It’s thought] time travelers can do less than we might have hoped: they cannot right the wrongs of history; they cannot even stir a speck of dust on a certain day in the past if, on that day, the speck was in fact unmoved. But this does not mean that time travelers must be entirely powerless in the past: while they cannot do anything that did not actually happen, they can (in principle) do anything that did happen. Time travelers cannot change the past: they cannot make it different from the way it was—but they can participate in it: they can be amongst the people who did make the past the way it was.

I loved the idea — in a book about tweenage heroes who can transcend most of the laws of physics by saying a nonsense word while waving an overpriced stick — that one thing that was inescapable for the characters was time, that even though they could travel backward through it to do all their extra homework and save the world, time was still for them a source of inevitability, and that they had to work with rather than against it. When Hermione reveals that she’s been using a time-turner, and then she and Harry (per Dumbledore’s guidance) go back in time to save a magical turkey and Harry Potter’s godfather, suddenly all of the mysterious occurrences from the previous few scenes begin making sense: a hidden Harry and Hermione from the future were actually puppeteering everything. This even comes as a surprise to the future Harry and Hermione, who slowly realize that they sealed their own destiny: they’ve already seen a past dictated by their future presences in it, and through the properties of a causal loop, it means they’re absolutely destined to do what they’ve already seen themselves do.

This sequence allowed for one of the books’ most beautiful revelations: as Harry nearly has his soul leeched at the hands (or drippy fabrics) of the Dementors, a stag-shaped Patronus from the distance charges toward them and wards them off — and Harry is almost certain that from that direction, he can see his father. It’s of course a highly sentimental sight, and one that leaves Harry baffled and excited. Later, when Harry travels back to that scene, he finds himself waiting an uncomfortably long amount of time to bystand as his father saves his previous self: and then it dons on him that his father won’t be showing up. It was himself that his past self had seen, not his father. So as past-Harry gets mighty close to being de-souled, future-Harry takes the initiative and sends a Patronus — his first full Patronus, and a stag, just like his father’s — to save his past self. Because the book’s narration is third person limited, it allows us to chronologically see the scene through the eyes of both iterations of Harry, witnessing twice that reunion of self with self. I can’t imagine a more breathtaking passage of self-actualization in a children’s novel.

An impressive blend of dejecting and emboldening, the passage suggests that the only true reawakening of the dead can ever occur within ourselves, as composites of the dead’s imprinted affections. The crux of the whole series is that Harry’s superlative abilities stem from his mother’s final gesture of maternal love, and here Rowling used time travel as merely another means of expressing the past as something that embeds itself in us.

Even as an atheistic reader — or perhaps more so as an atheistic reader — there was something refreshingly, mythologically simple to the singular path between past, present and future presented in the book — as opposed to the more vulnerable nature of time in Cursed Child. Channeling a somewhat religious notion of fate into a deeply humanist plot line, Prisoner of Azkaban turned both time and inevitability into the characters’ collaborators. They had to go back in time, because the events their time travel would eventually catalyze had already happened. Rather than opening the possibility of infinite alternate universes and thus lessening all sense of consequence, Harry Potter and the Prisoner of Azkaban stuck to a notion of the inalterability of the past. It spoke directly to one of the lovely ontological paradoxes of the Harry Potter novels: that there was a level of inevitability, but that it was fueled by the bravery and love within individuals. The grand, overarching narrative that determined itself through prophecies — and particularly one prophecy, delivered by Sybill Trelawney — is, oddly, simultaneously one of heroic personal agency.