Tom Riddle's Diary: Voldemort's First Horcrux Explained

Voldemort could have hidden a piece of his soul in a fortress, in a vault or at the bottom of the sea. He put it in a school notebook. A cheap notebook, bought at a stationery shop in London, which years later ended up in the cauldron of an eleven-year-old girl.

It's the first of the seven Horcruxes and, if you think about it, the strangest of them all. The others are hiding places. This one talked.

What a Horcrux Is and What One Costs

A Horcrux is an object where a wizard keeps a fragment of his soul. As long as that object exists, the wizard can't fully die. Dumbledore explains it to Harry in Half-Blood Prince (ch. 23), and the heaviest part is the price: the soul only splits through murder. There's no shortcut.

The key clue comes from a memory that Slughorn took years to hand over (ch. 17). In it, a sixteen-year-old Tom Riddle asks his teacher, perfectly calm, what would happen if someone split his soul into seven. He didn't want one Horcrux. He wanted several.

The Perfect Student

Before he had another name, Tom Riddle was an orphan in a Muggle orphanage. At Hogwarts he was a Slytherin prefect, a brilliant student and the favorite of almost every teacher. Almost. Dumbledore never fully believed him.

That facade matters for understanding the diary: Tom knew how to be liked. And the diary does exactly that.

How the Diary Was Born

In 1943, Tom opened the Chamber of Secrets and the basilisk killed a student in the girls' bathroom: Myrtle, the girl we later know as Moaning Myrtle. Dumbledore believes Tom used that death to create the diary (Half-Blood Prince, ch. 23).

The object itself was nothing special. Harry sees the label in Chamber of Secrets (ch. 13): a stationery shop on Vauxhall Road, in London. What was special was what it held inside. If you wrote on its pages, the ink vanished and someone wrote back. When Harry tries it, the diary pulls him into a memory from 1943 where he watches Tom accuse Hagrid. All of it calculated to make you trust him.

Ginny Weasley

Lucius Malfoy slipped the diary in among Ginny's books during the fight with Arthur Weasley at Flourish and Blotts (Chamber of Secrets, ch. 4). Ginny was eleven, in her first year and quietly in love with her brother's friend. She told the diary everything.

And the diary fed on that. Tom says so at the end, almost with relish: the more Ginny poured her heart out to him, the stronger he grew. She started losing chunks of time. She'd turn up with rooster feathers on her robes and red paint on her hands without knowing why. She was the one opening the Chamber, setting the basilisk loose, writing the messages on the walls.

When Harry goes down into the Chamber (ch. 17), Ginny is nearly dead and a sixteen-year-old Tom, more solid by the minute, is waiting for her.

How It Was Destroyed

Harry stabs a basilisk fang into the diary. Ink gushes from the pages, Tom screams and dissolves. Harry has no idea what he's just done. Dumbledore suspects something that same night, but the word "Horcrux" doesn't show up until four books later.

Book vs. Movie

How Harry finds the diary. In the book he finds it lying in Myrtle's bathroom, where it had hit her on the head when someone threw it (ch. 13). The movie keeps the scene, but loses the fun of Myrtle offended by the blow.
What Ginny did at night. The book makes it clear she killed Hagrid's roosters and painted the messages. The movie barely hints at it.
What the diary actually was. In the book, Dumbledore's explanation in Half-Blood Prince takes up several chapters of memories. In the movie it shrinks to a short conversation, and anyone who has only seen the movies misses the full logic.

What Almost Nobody Notices

Here is the part that unsettled Dumbledore most (Half-Blood Prince, ch. 23): the diary wasn't made just for hiding. It was made for someone to use, to possess whoever read it and reopen the Chamber. A piece of soul turned into a weapon.

To Dumbledore that made no sense. If you store your soul in an object, you hide it. You don't leave it in anyone's hands. That Voldemort entrusted it to Lucius Malfoy, without telling him what it was, is what showed Dumbledore there was more than one Horcrux. Nobody risks their only backup like that. You only risk one when you have several.

So the diary, besides nearly killing Ginny, was the first clue to the whole plan.

Where It Fits in the Series

A twelve-year-old boy destroyed the first piece without knowing what it was. Six remained. The next was a ring with a curse that would end up killing the most powerful wizard in the world, without Voldemort needing to be there. Continue with Gaunt's Ring: The Horcrux That Doomed Dumbledore.

And if you want to know which house the Sorting Hat would put you in, we have our house quiz.