Chamber of Secrets explained: who opened it and why Hogwarts blamed Hagrid

Lucius Malfoy (Jason Isaacs) gets the diary into Hogwarts the ordinary way, in a student’s belongings. During the row in the bookshop, he slips the diary into Ginny’s cauldron. His contempt for Arthur Weasley (Mark Williams) is loud enough to cover one small movement of the hand.

Ginny carries the danger into school herself.

Riddle explains what it does to her: “You see, as poor Ginny grows weaker, I grow stronger.” She has been in what he calls “a kind of trance”, and when the diary began to scare her, “She tried to dispose of it in the girls’ bathroom.” Lucius has turned a feud with a family into an attack on its youngest child.

Harry Potter (Daniel Radcliffe) can hear the basilisk in the walls because he understands Parseltongue. The rest of the school finds out he speaks it at the Duelling Club and starts to wonder whether he is the Heir of Slytherin.

The one boy who can hear the attacker becomes a suspect, so he keeps the voice from the adults. When Albus Dumbledore (Richard Harris) asks if there is “something you wish to tell me”, Harry answers, “No, sir. Nothing.”

Hermione Granger (Emma Watson) solves it in the library and is petrified before she can tell anyone. The page in her hand describes the basilisk, and the last word on it is “Pipes”. The basilisk has been moving through the school’s plumbing.

Its victims are petrified, not killed, because none of them met its eyes directly. They saw it through a camera, through a ghost or in a reflection, and the ghost was already dead.

The diary shows Harry a memory from fifty years earlier: Riddle catching Hagrid with a creature in a box and warning him, “You’ll be expelled.” Harry takes it at face value. Aragog (Julian Glover, voice), the creature from the box, now enormous, puts him right: “That’s a lie. Hagrid never opened the Chamber of Secrets.”

By then Cornelius Fudge (Robert Hardy) has already taken Hagrid to Azkaban, because “Hagrid’s record is against him.” The Ministry repeats the old mistake, and Riddle gets more time with Ginny.

In the Chamber, Riddle tells Harry the truth: “It was Ginny Weasley who opened the Chamber of Secrets,” because he told her to. Fawkes the phoenix brings Harry the Sorting Hat, the Sword of Gryffindor comes out of it, and Harry kills the basilisk, but one of its fangs goes into him as it dies.

Poisoned, he stabs the diary with the fang, and Riddle is destroyed. Ginny wakes and tells him, “I swear, I didn’t mean to. Riddle made me.” Fawkes’s tears heal Harry’s wound.

Dumbledore warns Lucius in general terms: “One hopes that no more of Lord Voldemort’s old school things should find their way into innocent hands. The consequences for the one responsible would be severe.” Harry is blunter: “I think you slipped the diary into Ginny Weasley’s cauldron, that day at Diagon Alley.” Lucius tells him to prove it.

Harry cannot prove it. He frees Dobby (Toby Jones, voice) instead: he hands Lucius the diary with one of his own socks inside, Lucius passes it to Dobby without looking, and Dobby opens it: “Master has presented Dobby with clothes. Dobby is free.”

The diary that nearly killed Ginny costs Lucius his servant.