Piers laughed again. "It's a word you don't understand, my Queen of all good fairies. It's only the naughty fairies—the will-o'-the-wisps and the hobgoblins—that know anything about it. It's a wicked spell concocted by the King of Evil himself, and it's only under that spell that his prisoners ever see the light. It's the one ticket of leave from the dungeons, and they must either use it or die in the dark."
Jeanie was listening with a puzzled frown, but Gracie's imagination was instantly fired.
"Do go on!" she said eagerly. "I know what a ticket of leave is. Nurse's uncle had one. It means you have to go back after a certain time, doesn't it?"
"Exactly," said Piers grimly. "When the ticket expires."
"But I don't see," began Jeanie. Her face was flushed and a little distressed. "How can hypnotism be like—like a ticket of leave?"
"I told you you wouldn't understand," said Piers. "You see you've got to realize what hypnotism is before you can know what it's like. It's really the art of imposing one's will upon someone else's, of making that other person see things as you want them to see them—not as they really are. It's the power of deception carried to a superlative degree. And when that power is exhausted, the ticket may be said to have expired—and the prisoner returns to the dungeon. Sometimes he takes the other person with him. Sometimes he goes alone."
He stopped abruptly as a hand rapped smartly on the door.
Avery looked up again from her work. "Come in!" she said.
"It's the doctor!" whispered Gracie to Piers. "Bother him!"
Piers laughed with his lower lip between his teeth, and Lennox Tudor opened the door and paused upon the threshold.