Let's talk about eagle owls for a moment.
I think we all know that the Malfoy family owns an eagle owl. We see it delivering packages of sweets to Draco early in the series and from time to time thereafter.
We also know that, in that pivotal vision that harry has in The Goblet of Fire of Voldemort, Wormtail and Nagini just before the third task, Harry arrives at the Riddle Manor House riding upon the back of an eagle owl.
But did you notice that J.K. mentions an eagle owl one other time, earlier in that same novel?
Having grown tired of Ron and Hermione's squabbling over the plight of house elves, Harry decides to go to the Owlery by himself to send a package of food to Sirius. After seeing Pigwidgeon and a couple of school owls off, he stands, looking out over the school grounds, the Durmstrang ship and the Forbidden Dorest, thinking.
Harry sees Hagrid busily digging a patch of ground outside his home and he also sees something else: an eagle owl that flies through the coil of smoke rising from Hagrid's house.
It's a beautifully written, calming scene, like a landscape painting that draws your eye into the world it depicts.
But it's also a clue. One I had not noticed in all of my previous readings of this novel.
The eagle owl is bringing messages back and forth between Barty Crouch Jr. at Hogwarts and Voldemort at the Riddle Manor House. It has to be. It's the Malfoy eagle and it's being used as part of the plot against Harry.
Harry's subconscious mind recognises it as a clue and inserts the eagle owl into his vision. Instead of a message, the owl brings Harry to Voldemort.
When I finally noticed it, I couldn't help but to be impressed, once again, with Rowling's skills as a writer and the very carefully thought and planning she put into every novel.
I've always been amazed at how subtly she inserted a bug into every scene of this book where Rita Skeeter (whom we later discover to be an animagus) eavesdrops on conversations; I never noticed this lovely and subtle clue which should have told me, at least given me a clue as to who was plotting against Harry at Hogwarts.