"Do you promise you won't hurt me?" asked Arthur.
"You will be safe from all harm for the space of a quarter hour, as measured by this clock," replied the Old One. "You are mortal enough that I would not slay you like a wandering cockroach, or a Denizen of the House."
"Thanks," said Arthur. "I think."

p. 67. - The Keys to the Kingdom series - Superior Saturday (2008)