“We’ll have to break the lock. It may even be Alex in there. But whoever it is, they need help.”
“I suppose we just imagined that it came from the ground,” said Joan. “Perhaps the echo sounded along under ground, some way.” It didn’t seem possible, but this had been such a stirring, mysterious sort of night that anything at all might happen.
“Um.” Chub was banging away at the lock on the back door. It wasn’t really locked after all, just held fast with a stout stick, that had to be knocked out of place. Thump, thump sounded over the clear, night air. There, the door swung open, emitting a gust of damp, unused air. It took nerve to go through the empty place, with only the moonlight to guide them—especially a place that had once housed ill people. There still hung an unearthly, hospital smell about it. Joan kept close to Chub, who stalked about each room, calling, “Any one here?” in a voice that did not quaver. There was never any reply, and finally they had been in every room.
“No use,” decided the boy, and they started toward the back door. Then it came again, the low moan, only it sounded farther away than ever now, and certainly seemed to come from underneath the ground. “The cellar!” Chub led the way down the dark, narrow stairs, feeling for each step. But the place was empty.
“Why, the subway tunnel!” Joan remembered. “I never thought of it until now.” Then she explained, “It’s connected with the main building.”
“But can we find the opening?”
They began to feel around the wall of the room they were in. It was a small cellar, and had apparently at one time been used as a kitchen or laboratory. By an old sunken sink, which gleamed in the dimness like a tooth in a darky’s mouth, a part of the wall moved under their pressure and swung inward, into an opening.
“Hot dog!” cried the boy. “All the earmarks of a real detective story. Sliding panels and everything.”
“It doesn’t slide, and it isn’t a panel,” objected Joan, as she watched him step into the darkness of the aperture. “Oh, dear, I don’t know whether to go or not. If we only had a flashlight or even matches. I feel like Alice in Wonderland! Oh, wouldn’t this be a wonderful place for a person to hide, like that bookkeeper I read of—Richard Marat?”
“It’ll be a good place for Dummy to hide in after we prove him a spy,” conceded Chub’s voice from within the depths. Then he halloed ahead, “Anybody here?”