They continued on. Curtis took the lead with the lantern, and Prue scraped along behind him. The tunnel was not yet tall enough to stand in; they remained on all fours, though their knees and palms were beginning to smart. Curtis could see Septimus in the barely visible distance, hopping along through the small tunnel as if it were a second home to him.
After traveling this way for a time, Curtis saw the rat come up abruptly at a sharp turn in the passage. He cocked his head and looked at the two children. “Listen,” he said. “Do you hear that?”
Prue concentrated. “No,” she said. “What is it?”
“It’s like a … I don’t know … slushing sound,” Septimus said cryptically. Shrugging, the rat continued on into the darkness.
Curtis crawled a few more feet forward, and the ground below his knees promptly gave way.
He fell.
It would be a stretch to say that Prue saw it happen; more like: She saw him there, in front of her, and then he was simply not there anymore. It was like he’d vanished.
“CURTIS!” screamed Prue. She was petrified, too scared to move.
A loud splash.
“That’s what I heard,” said Septimus, peering over the break in the tunnel. “Water.”
Prue ignored the rat. She yelled Curtis’s name again, mustering all the volume she could manage. The tunnel rang with the sound.
A surprised yelp met her cry. “WATER!” Curtis shouted back, shrilly, from below. “COLD WATER!”
Luckily, the lantern had not fallen with him; it remained, tipped sideways, in the narrow tunnel. Prue grabbed it and swung it in front of her, trying to get her bearings. There was a gaping hole in the rock directly in front of her; it was roughly Curtis-sized. Oddly, the edges of the hole seemed to be angular, though the reason behind this did not immediately occur to Prue. She was too focused on the well-being of her friend.
“Are you all right?” she called to Curtis.
“Y-yeah!” he sputtered. His voice reverberated eerily; it occurred to Prue that it was the voice of someone occupying a very large space.
“What happened?”
“I fell into this—this pool!” he called. There was some more frantic splashing. “It’s really cold!”
“Hold up,” Prue called. “I’m going to try something.” She cocked an eyebrow at Septimus. Her tongue fixed between her lips, she quickly unspooled the rope from her bag. Once she had it in hand, she waved the rat toward her.
“Hold on to this,” she said, handing him the lantern.
He did as she instructed, though he eyed her warily as she tied the end of the rope around his belly and pushed him toward the hole in the floor.
“I got it,” he reassured. “I got it.”
Light began to flood the lower chamber once the rat had been dangled into the orifice. Septimus squirmed uncomfortably against the rope at his waist but continued to hold tight to the lantern.
“Over here, Septimus! Keep it c-coming!” Curtis shivered. “I can start to see … There!” There came more splashing; Prue peered over the edge of the hole and saw her friend swimming, frantically, in the middle of a vast pool of jet-black water. The light, cast backward toward the hole he’d fallen through, illuminated in silhouette the distinct pattern of brickwork, like a collapsed wall on some old abandoned house.
Curtis let out a loud gasp of relief. “God, that’s cold,” he yelled. He’d reached dry land.
“You guys,” shouted Septimus. “Look at this.”
Prue peered her head over the edge of the hole and found the rat’s swaying shape. The lantern light was dim, but she could see it illuminating the space as the rat swung it about his head. “It’s a chamber of some sort. Man-made!” She felt at the break in the tunnel floor—felt the cool, damp roughness of the bricks. She must’ve gotten overzealous in her inspection, as the mortar crumbled again and Prue went crashing, rat, rope, knapsack, lantern and all, into the giant pool.
The water was positively freezing; Curtis’s shrieks had even undersold it. She felt a lightninglike bolt fly through her body, from her feet to her head, as she plunged into the cavern pool. The lantern was immediately extinguished; it was like someone had thrown a black shroud over the world. For a second, she floated in the black fluid, feeling the frigid water find its way into every fold of her clothing. She felt suspended there, like some ancient insect hovering in amber. And then she exploded to the surface, gasping for air.
“PRUE!” she could hear Curtis shout.
She was having a hard time getting air into her lungs. Her whole body was searing with sharp, cold pain. She hiccuped; she gasped.
“Over here!” yelled Curtis. She desperately swam for the source of the sound.