The Basilisk was very cranky after being awoken from sleep. The words it was hearing harkened back to some that were spoken to it ages past.
"I am the heir of Salazar Slytherin. I command you to help me cleanse this school of the Mudbloods and filth threatening it from without."
This is what the King of Serpents heard.
When it was born, its master and creator had told it all of how the school was at risk from "external threats" and that its purpose was to protect the school from said threats.
But over time, the serpent knew, it had been proven that there were no such threats as the master had believed.
Indeed, the serpent thought, what was now threatening the school's populace was … this boy declaring himself the master's heir.
There was only one acceptable course of action, the serpent knew. The master had been clear: threats were to be dealt with.
Quicker than it was possible to be believed, the serpent whipped its head around and snapped, piercing the dangerous boy nearly all the way through his torso with both major fangs, and injecting a full load of venom into him.
The venom would have caused a fatality even if the bite had not already inflicted a mortal wounding.
Fifteen year-old Tom Marvolo Riddle died in agony within thirty seconds.
Noting the corpse was of adequate size for consumption, the serpent swallowed it.
The fifth-year boy's absence was first noted by his head of house, Horace Slughorn, that evening as Tom had failed to report for the house prefect's meeting.
When the open portal in the girls' lavatory was alerted to the Headmaster and Deputy, an expedition was mounted. The opened Chamber of Secrets, heretofore a myth, was found in minutes. No remnant of Tom Marvolo Riddle ever was.
It was concluded by Headmaster Armando Dippet that the boy scarpered over pressure of his looming Ordinary Wizarding Levels.
Deputy Headmaster Albus Dumbledore had a different theory, but neglected to mention it.
Horace Slughorn lamented Tom's absence. No one else did.
Some decades later an exceptionally gifted and powerful student named Harry James Potter finished his N.E.W.T exams with record scores in Charms, Transfiguration, and Defense. It was also recorded that, due to Mr. Potter's fluency and frequency of pranks, that Gryffindor House finished dead last in the running for the House Cup every year he attended, never finishing with even a single point.
Potter married a Ravenclaw from the academic year following his, and never paid a thought even at the end of his long life to the fact that he had never once appeared in the newspapers, for any reason.