Harry Potter fans, get ready to hear an incredible fan theory about the link to Fantastic Beasts And Where To Find Them.
Author JK Rowling's latest work adapted to screen may be a completely independent tale to the world of Potter, but like all of the best fantasy universe spin-offs, there just had to be a connection somewhere for those who looked hard enough.
Well, according to Harry Potter superfan Jackson Bird - whose title at non-profit organisation the Harry Potter Alliance is, amazingly, Director of Wizard-Muggle Relations, the link is definitely there - although if you haven't read The Deathly Hallows or Fantastic Beasts, you might want to look away now.
Speaking to ScreenCrush, he explained how he had gone through the books with a fine tooth comb and realised that an obscurus, the threat that Newt Scamander has to face in Fantastic Beasts, actually reared its head in the final Potter instalment.
An obscurus is an unstable dark force that bursts out of somebody trying to suppress their magic, which grows stronger the older the person gets.
In Harry Potter And The Deathly Hallows, Albus Dumbledore's brother Aberforth said of their sister Ariana: "It destroyed her what they did, she was never right again. She wouldn't use magic, but she couldn't get rid of it. It turned inward and drove her mad, it exploded out of her when she couldn't control it and at times she was strange and dangerous."
So that could be where Grindelwald first learned about the obscurus, and how he knows so much about it when he is investigating it in the US as Percival Graves.
Sounds like it's time for yet another re-read of the Harry Potter books...