Harry felt like something had yanked his soul clean out of his body.
Everything went fuzzy. The walls doubled, the sinks gurgled like they were underwater, and every sound arrived five seconds late.
"No way…"
He dropped the alchemical frog into his palm, slammed the basilisk fang onto the diary, and snarled,
"Tell me how to get inside!"
The diary didn't move.
"Let me try."
Ron grabbed it and yanked with everything he had. Nothing. Not even a tear. Whatever magic was on that thing, it wasn't letting go.
Breathing hard, Ron set the diary on the edge of the sink. A battered old quill was still stuck between the pages. The second the quill touched the paper, ink sank in like it was being drank, and words bloomed across the page:
[Speak "open" in Parseltongue.]
…
They didn't have time to think twice.
Hermione bolted for Dumbledore's office. Harry and Ron threw themselves down the pipe after the diary.
The tunnel was dead silent, the kind of silence you only find in tombs. The only sound was a sharp crack—Ron had just stepped on a rat skull.
Harry lowered his wand. The floor was carpeted with tiny animal bones.
He tried very hard not to picture what had happened to their owners.
The basilisk was out. Sean's alchemical creatures had all been petrified… so what about Sean…?
Harry broke into a run, skidding around a dark corner.
"Harry, there's something—" Ron croaked.
They froze.
At the far end of the tunnel lay a coiled something enormous and motionless. Wand-light glinted off vivid green scales—an empty snakeskin, bright as poison, at least twenty feet long.
Their stomachs dropped straight through the floor.
They ran again, lungs burning, until the tunnel finally opened into the long, dim chamber lined with stone serpents.
Harry dripped ink into the diary again and brandished the fang.
"Where's Sean?"
The book shivered.
[Finally took the bait. Took way more effort than I expected to nudge you lot…
That guy you mentioned is a real pain. Even I couldn't finish him quickly.
But he was never the target. You are, Harry Potter.]
"What do you mean, no, where is Sean?!"
[That fang… interesting. Doesn't matter. You walked right in.
As for your friend… if he came down here? Heh. He's probably dead by now.
But I've got plenty of questions for you first, Harry Potter.]
Ron sat down hard on the slimy floor, looking like he'd been struck by lightning.
Harry couldn't see straight. With a roar he drove the fang straight through the diary.
A long, piercing shriek tore through the chamber as ink exploded out, soaking Harry's hands and splattering the stone. Then a dark shadow rose in front of him.
"You asked for it!" the shadow hissed.
"Speak to me, Slytherin, greatest of the Hogwarts Four!"
The gigantic stone face of Salazar Slytherin moved. Its mouth opened wider and wider until it became a cavernous black void.
Harry raised the fang again.
"I've been waiting, Harry Potter!"
The shadow twisted and screamed, flailing as it unraveled.
Harry and Ron squeezed their eyes shut.
"RUN!" Harry yelled.
And immediately crashed into something solid.
"Harry?"
That voice—impossibly familiar.
Harry opened his eyes.
Sean was standing right there, looking mildly confused, like Harry had almost walked into a pillar.
"Sean…? Am I dead after all…? I'm so sorry, we got here too late…"
Harry turned. Ron was on the floor too.
Ron was dead as well…
Ron's reaction was even more dramatic—he took one look at Sean, rolled his eyes back, and passed out cold.
"You're not dead, Harry," Sean said, deadpan.
He'd followed the Marauder's Map down here and arrived just in time to watch Harry stab Tom Riddle's diary halfway to death.
He glanced at the smoking, hole-riddled book. Venom was still eating through the pages, black smoke curling up from the wound.
From the hole, a faint, furious voice rasped, "Impossible… how did you deal with the basilisk…?"
Sean met the shadow's eyes. Two seconds later Tom let out an enraged howl of rage and vanished into nothing.
Once Riddle's influence was gone, the diary became just a diary again. Sean flicked his wand; the pages flipped themselves open. He spotted Hagrid's name instantly.
[Stupid oaf Hagrid, clumsy as ever, always causing trouble. Once a week he gets himself into a mess every week, raising werewolf cubs under his bed, wrestling trolls in the Forbidden Forest…
Honestly, even I didn't expect the plan to go this smoothly. I was sure someone would realize Hagrid could never be Slytherin's heir.]
Looks like Hagrid's getting out of Azkaban, Sean thought.
"Sean?" Harry finally seemed to catch up with reality. "You beat the basilisk?"
Sean gave a small nod.
Harry's knees nearly gave out. Relief hit him so hard his eyes went red and watery all over again.
"Seems you two did pretty well yourselves," a calm, kindly voice said behind them.
Ron stirred, sat up, and saw Hermione standing next to Dumbledore.
For one glorious second he was convinced the entire wizarding world was dead.
"Hermione, you're dead too…?" he whimpered.
Hermione punched him in the chest. Hard.
"I'M NOT DEAD!"
"Oh—right—haha…" Ron went scarlet and tried to melt into the floor.
Dumbledore just twinkled, looking far too amused for someone standing in the Chamber of Secrets next to a half-destroyed Horcrux and two unconscious teenagers.