One of the best things about Harry Potter is how many hints about the big twist at the end are woven into the story so subtly that they seem unimportant. For example, in the first five chapters of Chamber of Secrets, it’s obvious that someone is plotting something. Dobby tells us as much. It’s much easier to miss the little hints already being planted about who, what, and how. Things like …
- Lucius Malfoy telling Mr. Borgin, “I have important business elsewhere today”. The next time we see him, he’s busy sneering at the Weasleys, not what most people would describe as “important business”.
- Borgin’s comment that “if the stories are true, you haven’t solf me half of what’s hidden in your manor”. The secret plot involves one very important object of his, much darker and more dangerous than what he sold to Borgin. Dumbledore later explains that Mr. Malfoy was likely worried about the diary being discovered and unaware of its true nature, simply believing it was enchanted to open the Chamber of Secrets again.
- Mr. Malfoy is ashamed of his son, Draco, because “a girl of no wizard family” beat him in every exam. This question of who deserves to learn magic has barely been touched on at this point, but it’s about to be brought directly into focus.
- Malfoy later takes “a very battered copy of A Beginner’s Guide to Transfiguration” from Ginny Weasley, presumably to mock the Weasleys’ inability to buy new books, and hands it back a few minutes later. In the movie, they actually show one book coming out of her cauldron and two going back in.
- As they’re in the car on their way to London, Ginny realizes she forgot her diary and insists that the family go back for it.
Those hints mean very little to a first-time reader. They’re buried among other more mundane details, for one thing. Nothing ever comes of Fred and George having to go back for a box of fireworks and a broomstick, and while the scenes in Knockturn Alley contain many hints at things to come in Half-Blood Prince, they’re also full of details that don’t ever become important, such as the poisons Mr. Malfoy is selling and the “evil-looking masks” on the walls of Borgin and Burke’s. But on a careful re-read, they’re all there. The whole story of how Ginny got the diary and what it was meant to be used for is there, in a few passing remarks and seemingly-unimportant lines. The twist ending is shocking, but it does not come out of nowhere.