WHO: The Inner Circle
WHEN: 31 January 1943, past curfew.
WHERE: Second floor girls' bathroom, then the CHAMBER OF SECRETS.
WHAT: Being shits.
Soundtrack.
Just as Potions ended, each of the Inner Circle members would have discovered a piece of parchment on top of their notes. In Tom's writing, it said:
If you wish to enter the Chamber: 10:15 PM, second floor girls' bathroom. Disillusion yourselves.
After they had left the classroom and read it twice, the note dissolved into a puff of smoke. Sucks for you if you forgot what it said!
At the appointed time, Tom was waiting in the bathroom. Because he waited for everyone to arrive, he was lurking, Disillusioned, in a corner. Because he was nearly invisible, he probably gave them all a bit of a fright when he seemed to appear out of nowhere. But that's What Tom Does.
After this, he Opened the Chamber, so that the sink in Myrtle's bathroom opened into a tunnel. This required speaking Parseltongue, which the IC has seen him do before, but without a snake, probably sounds very creepy. Tom floated lazily down the tunnel, but the other boys could have slid down if they preferred to take Hogwarts' biggest, dirtiest slippy slide.
At the bottom, Tom had cleaned up
most of the bones littering the Chamber, though already they were beginning to accumulate again. He made the IC wait in the antechamber while he told the basilisk to keep her eyes closed, as he had friends here and some of them could be rather dim.
Then, he let them into the great cavern with the statue of Slytherin and the giant snake, and they, IDK, frolicked and tried Cruciating some mice running around.