In the story of "Theseus and the Minotaur" from Greek mythology, Theseus succeeds in killing the Minotaur and, with the help of Ariadne, is able to escape the labyrinth. Theseus' escape plan involves a ball of string, or clew, given to him by Ariadne. By tying the string at the entrance of the labyrinth and unwinding it as he walks, Theseus is able to retrace his path to escape the maze after killing the Minotaur. This is the origin of the word clue: evidence used to solve a mystery.
Despair enters the story when Theseus forgets his promise to his father, Aegeus, that if he killed the Minotaur he would hoist white sails, rather than black ones, on his return trip to Athens. Seeing black sails, Aegeus believes his son is dead and throws himself from the high cliffs to the sea below. The sea thereafter became know as the Aegean Sea.
We might also reserve a place in the Ideas Hall for Theseus under "memory" since in his jubilant spirit of victory he fails to pay attention to detail and forgets to change the sails.
Question: How does a ball of string relate to the clue followed by a detective?