"And she provided him besides with a ball of thread,
bidding him to fasten the end of it to the entrance
of the Labyrinth, and unwind it as he went in, that
it might serve him as a clue to find his way out again."
— "Theseus and Ariadne," by Charles Morris
From "Ariadne's Clue," a post of March 1 last year—
The Watson here is not Emma, but Victor—