Quote from : Thief of Time Book

That was a !" he said. "An evil spirit! The peasants down in the valleys hang up charms against them! But I thought they were just a superstition!" "No, they're a substition," said Susan. "I mean they're real, but hardly anyone really believes them. Mostly everyone believes in things that aren't real. Something very strange is going on. Those things are all over the place, and they've got . That's not right. We've got to find the person who built the clock - " "And, er, what are , Miss Susan?" "Me? I'm...a schoolteacher." She followed his gaze to the wrench that she still carried in her hand, and shrugged. "It can get pretty rough at break time, can it?" said Lobsang.