Ariadne's thread

Beneath the palace of King Minos on Crete lay the Labyrinth — a maze so vast and so cunningly twisted that no one who walked in ever found the way out. And at its dark heart waited the Minotaur, a monster half-man and half-bull, to whom young men and women were sent as living tribute.

The hero Theseus came to Crete determined to kill the beast and end the horror. But even a hero could see the trap: he might slay the Minotaur and still wander the endless corridors until he starved, lost forever in the turning dark.

The king's daughter, Ariadne, watched him and fell in love. On the night before he entered, she pressed into his hand a simple thing — a ball of thread. Tie one end at the entrance, she told him, and let it out behind you as you go, however deep you must travel.

So Theseus walked into the Labyrinth unspooling the thread step by step, deeper and deeper into the maze until he came upon the Minotaur and killed it. And then, with no landmark to guide him in that stone wilderness, he simply followed the thin thread back through every turn — and walked out into the light.

Ever since, Ariadne's thread has meant the clue, the method, the single guiding line that leads a person safely out of a problem so tangled it would otherwise swallow them whole.