Forward:

Thank you for checking out my new story! It's going to finish around 22K words and 16 chapters, and I plan on posting a new chapter every week by the end of Friday.

NOTE: This is an AU where Horcruxes work a little differently than they do in canon. This choice is intentional. This details will become clearer as the story goes along.

Tom Riddle's Freaky Friday was inspired by the idea that if 16 year old Tom Riddle had succeeded in returning to physical form in Chamber of Secrets, then once Voldemort had risen from the graveyard in Goblet of Fire, two rival Dark Lords would be competing for power at the same time—which certainly complicates things for Dumbledore!

If this point of departure has been explored by others before me, I'm confident this journey will be unique. Like the movie Freaky Friday, the story is full of situational humor and fun around mistaken identity, while also playing out a strategic cat-and-mouse game between geniuses in the vein of the anime Death Note. I hope it will appeal to fans of rational fiction like Harry Potter and the Methods of Rationality, even as it's not strictly in that genre.

Writing this story helped me break through a decade of avoiding prose. I put a lot of myself into it, and now I daresay it's one of my favorite things I've ever written. I will read and appreciate all reader comments. Without further ado, I hope you enjoy Tom Riddle's Freaky Friday.

Chapter One: Freaky Friday

Tom Riddle spun around with his wand at the ready, prepared to wipe the girl's memory.

He had assumed no other student would dare break curfew—Headmaster Dippet was known to hand out corporal punishments for the infraction—but here was a girl in the second floor bathroom stall, having come to cry alone or something.

Unlucky for her, she had witnessed him summon the Basilisk of Salazar Slytherin—the giant serpentine monster—from the castle's Chamber of Secrets, whose entrance was hidden here on the second floor girls' lavatory of all places.

Tom formed the word obliviate in his mind but before he could cast the memory spell, the girl fell out of the bathroom stall and slumped to the ground, unmoving.

Using magic so as not to touch her, he rolled her face up. Her identity flashed in his mind, thanks to all the hours he had spent mastering the names of every witch and wizard in Hogwarts. This was Myrtle Warren, Ravenclaw, fourth year—she was dead. She must have made eye contact with the Basilisk. Fatal mistake.

Tom had never killed anyone before. He still hadn't, technically, but the Basilisk was under his magical control, so he supposed that meant he was responsible for the death. It wasn't how he had planned to commit his first murder.

I hate when things don't go according to plan.

There would be an investigation, of course. Aurors would be sent from the Ministry's Department of Magical Law Enforcement to find the killer. Would they link it to him? Not if he could cover his tracks, frame someone else first. Before those plans had a chance to formulate in his mind, however, a more exciting thought occurred—

Why waste this opportunity? This was a solid death. He could use the magical potential of Myrtle's demise to create a Horcrux!

It was something he'd wanted to test out ever since he'd gotten Professor Slughorn drunk enough to tell him about it. The spell would split his own soul and imbue one piece to a physical object for safeguarding. As he understood it, the object could then be used to revive his body in the event that he should die. The trick was to find a servant trustworthy enough to carry out the resurrection, and Tom already had plenty of such followers in his secret society, the Death Eaters. But that part didn't matter just yet. First, he had to make the Horcrux. He knew he had to hurry while Myrtle's death was still fresh.

He patted his pockets. There wasn't much to make it with. Just his robes, some potion ingredients, and a leather-bound diary. None of these were ideal. He would have preferred something metal, jeweled, an heirloom that would not decay or decompose. But he was running out of time. To hell with it—the diary would have to do.

Giddy with excitement over his experiment, Tom set the book down beside Myrtle and stepped back. He took a deep breath to make sure his voice would be clear, then he spoke the long, forbidden incantation.

A green jet of energy erupted from his wand and engulfed Myrtle, himself and the diary in a blinding flash.

Tom opened his eyes.

As far as he could tell, he was no longer standing. Nor did he seem to be in the second floor lavatory anymore. He was staring at the canopy of a four poster bed.

What happened?

He sat up from a nest of pillows. He was in a red circular room with four other poster beds. Windows looked out at the castle rooftop. Am I inside Gryffindor Tower? If things had gone wrong, he would have expected to wake up in the Hospital Wing, or his own bed, not here in the dormitories of his rival house.

He fumbled for his wand but didn't find it in his robes because—Am I wearing a night gown? His body felt different too… slimmer.

The diary. There it was on the night table. A wand sat next to it, but it was not his own.

He reached out to take it, but did not recognize the small, pale fingers of his hand.

Oh no.

He got out of the bed and approached the mirror. He did not see the tall, handsome sixteen year old boy with raven hair that he expected. Instead, the mirror reflected back a thirteen year old red-haired girl with fair skin and freckles.

Unidentified girl. Gryffindor. Third Year. Oh no.

The spell had gone terribly wrong, hadn't it?

Had he transferred his soul into the diary, leaving his body behind? Instead of a soul split, had he only achieved a soul departure? Had it resulted in the possession of this unfortunate girl who had used the diary, divulged her secrets, made herself vulnerable to it?

Was this because I killed Myrtle indirectly?

Damn him and his split second decision to make a Horcrux! He should have waited until August to do it properly, when he'd planned to kill his own muggle father.

He looked at the four other girls fast asleep in their beds. None were his contemporaries at Hogwarts. Oh no.

Doubts creeped in. An unsettling thought.

There is another possibility.

What if the spell had gone right?

What if he had successfully split his soul, and… he was the split piece? What if the original half of his soul got to remain in his body and continue living out his life—while he was trapped here?

That wasn't how Horcruxes were supposed to work, was it? That would be more akin to… cloning. Creating a twin. Tom had thought of it more as a failsafe against dying, awarding oneself extra lives like a character in a muggle video game. Of course not much was really known about Horcruxes. None had been made for centuries, after all. It was entirely possible that he had been wrong about how they worked.

Well crap.

Professor Slughorn hadn't been kidding when he said dark magic wasn't to be trifled with.

Yes, the spell had certainly been a mistake. Now he was trapped in a waking nightmare. He was… Girl. Gryffindor. Third Year.

With freckles.

He shivered at the thought of it. Or was it the cold? Frost did line the windows… and a light snow had begun to fall outside them. Snow in June? When was this?

Although it was still dark, the morning chimes sounded and the other girls stirred awake, yawning and stretching.

One of them must have been hungry, because she shouted "Breakfast time!"