Just wanted to post the real story.

By the Brothers Grimm:

Once upon a time...
on the banks of a great river in the north of Germany lay a town called Hamelin. The citizens of Hamelin were honest folk who lived contentedly in their Grey stone houses. The years went by, and the town grew very rich.
Then one day, an extraordinary thing happened to disturb the peace.
Hamelin had always had rats, and a lot too. But they had never been a danger, for the cats had always solved the rat problem in the usual way- by killing them. All at once, however, the rats began to multiply.
In the end, a black sea of rats swarmed over the whole town. First, they attacked the barns and storehouses, then, for lack of anything better, they gnawed the wood, cloth or anything at all. The one thing they didn't eat was metal. The terrified citizens flocked to plead with the town councilors to free them from the plague of rats. But the council had, for a long time, been sitting in the Mayor's room, trying to think of a plan.
"What we need is an army of cats!"
But all the cats were dead.
"We'll put down poisoned food then . . ."
But most of the food was already gone and even poison did not stop the rats.
"It just can't be done without help!" said the Mayor sadly.
Just then, while the citizens milled around outside, there was a loud knock at the door. "Who can that be?" the city fathers wondered uneasily, mindful of the angry crowds. They gingerly opened the door. And to their surprise, there stood a tall thin man dressed in brightly colored clothes, with a long feather in his hat, and waving a gold pipe at them.
"I've freed other towns of beetles and bats," the stranger announced, "and for a thousand florins, I'll rid you of your rats!"
"A thousand florins!" exclaimed the Mayor. "We'll give you fifty thousand if you succeed!" At once the stranger hurried away, saying:
"It's late now, but at dawn tomorrow, there won't be a rat left in Hamelin!"
The sun was still below the horizon, when the sound of a pipe wafted through the streets of Hamelin. The pied piper slowly made his way through the houses and behind him flocked the rats. Out they scampered from doors, windows and gutters, rats of every size, all after the piper. And as he played, the stranger marched down to the river and straight into the water, up to his middle. Behind him swarmed the rats and every one was drowned and swept away by the current.
By the time the sun was high in the sky, there was not a single rat in the town. There was even greater delight at the town hall, until the piper tried to claim his payment.
"Fifty thousand florins?" exclaimed the councilors,
"Never..."
" A thousand florins at least!" cried the pied piper angrily. But the Mayor broke in. "The rats are all dead now and they can never come back. So be grateful for fifty florins, or you'll not get even that . . ."
His eyes flashing with rage, the pied piper pointed a threatening finger at the Mayor.
"You'll bitterly regret ever breaking your promise," he said, and vanished.
A shiver of fear ran through the councilors, but the Mayor shrugged and said excitedly: "We've saved fifty thousand florins!"
That night, freed from the nightmare of the rats, the citizens of Hamelin slept more soundly than ever. And when the strange sound of piping wafted through the streets at dawn, only the children heard it. Drawn as by magic, they hurried out of their homes. Again, the pied piper paced through the town, this time, it was children of all sizes that flocked at his heels to the sound of his strange piping.
The long procession soon left the town and made its way through the wood and across the forest till it reached the foot of a huge mountain. When the piper came to the dark rock, he played his pipe even louder still and a great door creaked open. Beyond lay a cave. In trooped the children behind the pied piper, and when the last child had gone into the darkness, the door creaked shut.
A great landslide came down the mountain blocking the entrance to the cave forever. Only one little lame boy escaped this fate. It was he who told the anxious citizens, searching for their children, what had happened. And no matter what people did, the mountain never gave up its victims.
Many years were to pass before the merry voices of other children would ring through the streets of Hamelin but the memory of the harsh lesson lingered in everyone's heart and was passed down from father to son through the centuries.

Extracts about the Pied Piper from Wikipedia:

In 1284, while the town of Hamelin was suffering from a rat infestation, a piper dressed in colorful red clothing appeared, claiming to be a rat-catcher. He promised the mayor a solution to their problem with the rats. The mayor in turn promised to pay him for the removal of the rats (according to some versions the promised sum was 1000 guilders). The piper accepted and played his pipe to lure the rats into the Weser River, where all but one drowned.

Despite the piper's success, the mayor reneged on his promise and refused to pay him the full sum (reputedly reduced to a sum of 50 guilders). The piper left the town angrily, vowing to return later to take revenge. On Saint John and Paul's day while the Hamelinites were in church, the piper returned dressed in green like a hunter playing his pipe. In so doing, he attracted the town's children. One hundred and thirty children followed him out of town where they were lured into a cave and never seen again. Depending on the version, at most three children remained behind: One was lame and could not follow quickly enough, the second was deaf and therefore could not hear the music, and the last was blind and unable to see where he was going. These three informed the villagers of what had happened when they came out from church.

Another version relates that the Pied Piper led the children into following him to the top of Koppelberg Hill, where he took them to a beautiful land and had his wicked way, or a place called Koppenberg Mountain, or that he made them walk into the Weser as he did with the rats, and they all drowned. Some versions state that the Piper returned the children after payment, or that he returned the children after the villagers paid several times the original amount of gold.

A number of theories suggest that children died of some natural causes such as disease or accident and that the Piper was a symbolic figure of Death. Analogous themes which are associated with this theory include the Dance of Death, Totentanz or Danse Macabre, a common medieval trope. Some of the scenarios that have been suggested as fitting this theory include that the children drowned in the river Weser, were killed in a landslide, or contracted some disease during an epidemic. Another modern interpretation reads the story as alluding to an event where Hamelin children were lured away by a pagan or heretic sect to forests near Coppenbrügge (the mysterious Koppen "hills" of the poem) for ritual dancing where they all perished during a sudden landslide or collapsing sinkhole.

Others have suggested that the children left Hamelin to be part of a pilgrimage, a military campaign, or even a new Children's crusade (which is said to have occurred in 1212) but never returned to their parents. These theories see the unnamed Piper as their leader or a recruiting agent. The town's people made up this story (instead of recording the facts) to avoid the wrath of the church or the king.