I'm perfectly well aware that you've found a doorway somewhere. I guess it's not too far from Summertown, where I dropped Lizzie, or Lyra, this morning. And that through the doorway is another world, one with no grownups in it. Right so far? Well, you see, the man who made that doorway has got a knife. He's hiding in that other world right now, and he's extremely afraid. He has reason to be. If he's where I think he is, he's in an old stone tower with angels carved around the doorway. The Torre degli Angeli.

Sir Charles to Lyra and Will, in Ch. 7 : The Rolls-Royce - His Dark Materials - The Subtle Knife (1997)