Voldemort had set his sights on the Philosopher's Stone. It was still sitting in a vault at Gringotts.
Gringotts boasted that it was the safest bank in the world and that nothing deposited there had ever been stolen.
Quirrell didn't buy it. There was no wall that couldn't be breached. If he couldn't break in from outside, he'd work from within.
First, Quirrell had to find out which vault held the Philosopher's Stone.
According to information Quirrell had bought on the Black Market, Nicolas Flamel seemed to have sensed trouble coming. He knew someone was after his Philosopher's Stone.
So the old man had entrusted it to his old friend, Albus Dumbledore, the headmaster of Hogwarts.
The Stone was now in Dumbledore's vault. But the location of each person's vault was one of Gringotts' most closely guarded secrets.
No one outside the vault's owner and the Goblins could get wind of it.
If Quirrell had the luck to find one vault among that vast underground maze, Voldemort would never have gotten him in his clutches in the first place.
To pin down Dumbledore's vault, Quirrell had paid a hefty sum to a Black Market dealer for a creature on the banned-sales list.
He dug an old leather suitcase out of his luggage. Its leather was worn and fuzzy. He flipped open the lid and gave two sharp whistles into it.
The whistles echoed inside. The suitcase had been enchanted with an Undetectable Extension Charm, giving it enormous capacity. Black Market smugglers loved using them.
It made a fine home for Fantastic Beasts, too. There was plenty of room for a wizard to set up a suitable habitat inside.
Before long, the suitcase trembled a few times, and a snow-white shape pushed its way out through the battered opening.
It was a fairly large white-furred Niffler. It turned its head to inspect its surroundings, its nose twitching. To look at it, the creature was exquisite.
But Quirrell knew exactly what sort of creature it was.
He hadn't had a kind thought about the adorable-looking beast since the moment he got it.
"The fuck? What kind of dump is this? Some pauper's place?" The white Niffler opened its mouth, and out came a stream of abuse utterly at odds with its lovely appearance.
The muscles in Quirrell's cheeks twitched. He kept reminding himself that he'd spent years of savings on this thing. He couldn't kill it.
He would need the foul-mouthed creature to get into Gringotts.
Even if he couldn't resist throttling it, Voldemort would never allow it.
The creature was called a Niffler. Found in Britain, Ireland, and North America, it could speak human languages and read human writing. With training, it could even handle simple questions and answers.
It had just one flaw: it was foul-mouthed by nature and loved nothing more than hurling abuse.
The Ministry of Magic gave it a low danger rating of just three crosses, but the little creature's ability to move through earth was frightening.
It could pass through most defensive magic as though it weren't there, which was why it had been placed on the banned-sales list.
Quirrell had bought this Niffler on the Black Market for a fixed price of over a thousand Galleons.
Most of what he'd saved during his years teaching Muggle Studies at Hogwarts had gone into that filthy mouth.
"Tonight, it's your turn to show what you can do." Quirrell grabbed the Niffler by the scruff of its neck.
"Get into Gringotts and find Albus Dumbledore's vault number."
"All right, all right, get your filthy paws off me, you son of a bitch!" the Niffler cursed as it struggled.
Nifflers sold on the Black Market were trained. They understood their owners' orders and carried them out reliably.
Their mouths were just too filthy. Why hadn't the dealers trained that habit out of them while they were at it?
Seething, Quirrell grabbed the Niffler and started to stuff it back into the suitcase.
The Niffler kicked like mad and shouted even louder. "It's time to let me out! Put me down, you bastard!"
Quirrell wanted to crush it then and there.
But the moment he thought of his mission and what he'd paid, his clenched fingers loosened.
He really couldn't refuse to let it out.
The seller had made that clear when Quirrell bought it: a Niffler couldn't be kept inside a suitcase enchanted with an Undetectable Extension Charm all the time.
It needed regular contact with real earth. Otherwise, it would grow listless and lose its ability to burrow.
The first few times Quirrell had let it out alone, he'd worried enough to follow it and keep watch.
But foul-mouthed as it was, the creature knew where home was. It had decided the suitcase was its den.
It was quick-witted, hard to catch, and fast on its feet. Each time, it had darted back into the suitcase ahead of Quirrell, who had been tailing it.
Eventually, Quirrell had stopped fussing. When the time came, he let it out to run wild on its own.
But this time... Diagon Alley was full of all kinds of people.
If the Niffler got lost here, he'd be out a fortune.
The Niffler in his hand glared at him as if to say, Let me out or I'll die right here.
Quirrell had no choice. He released his grip.
The instant the Niffler hit the floor, it slipped into a crack between the floorboards. Not a single hair remained in sight.
"Get your ass back here early," Quirrell called after it, staring at the empty crack.