"Where leads the Door? It leads outside our world," repeated Ennis. "What can that mean?"
"It might have a symbolic meaning, referring to some secluded fastness of the order which is away from the rest of the world," the inspector said. "Or it might——"
He stopped. "Or it might what?" pressed Ennis, his pale face thrust forward.
"It might mean, literally, that the Door leads outside our world and universe," finished the inspector.
Ennis' haunted eyes stared. "You mean that this Door might somehow lead into another universe? But that's impossible!"
"Perhaps unlikely," Campbell said quietly, "but not impossible. Modern science has taught us that there are other universes than the one we live in, universes congruent and coincident with our own in space and time, yet separated from our own by the impassable barrier of totally different dimensions. It is not entirely impossible that a greater science than ours might find a way to pierce that barrier between our universe and one of those outside ones, that a Door should be opened from ours into one of those others in the infinite outside."
"A door into the infinite outside," repeated Ennis broodingly, looking past the inspector. Then he made a sudden movement of wild impatience, the dread leaping back strong in his eyes again.
"Oh, what good is all this talk about Doors and infinite universes doing in finding Ruth? I want to do something! If you think this mysterious Brotherhood has taken her, you must surely have some idea of how we can get her back from them? You must know something more about them than you've told."
"I don't know anything more certainly, but I've certain suspicions that amount to convictions," Inspector Campbell said. "I've been working on this Brotherhood for many years, and block after block I've narrowed down to the place I think the order's local center, the London headquarters of the Brotherhood of the Door."
"Where is the place?" asked Ennis tensely.