The rocks of the pool floor shone green far below her, and silver fish flashed in the light. She was surprised by the depth of this water hole. She kicked toward the waterfall. Her vision was all but useless in the cascade of bubbles at its base, but she felt along the rocks with her hands and found, in the dark below the pouring water, a cavity that must be Po’s tunnel. She smiled, despite herself. She would never have found this secret place on her own; likely not a single person had ever done what she was about to do. She shot to the surface for a breath of air, then dived back down and pulled herself through the opening.

It was dark in this tunnel, black, and the water was even colder than the water in the pool. She could see nothing. She kicked forward through the tunnel and counted steadily. Rocks scratched her arms, and she felt in front of her with her hands to avoid cracking her head against anything unexpected. It was narrow, but not dangerously so. Po would have no trouble, if he were well enough to swim.

As her count neared the number thirty, the passageway widened, and then the tunnel walls disappeared all around. She shot upward, hoping to break through the surface, for she didn’t know where to find the air of this black cave if it wasn’t straight above. She was conscious now of her sense of direction, at which Po had always marveled. If she lost the tunnel in this darkness, and if she couldn’t find an opening to the surface, it was over for Katsa. But Katsa knew exactly where the tunnel was, behind her and below her. She knew how far she’d gone, and in what direction; she knew up and down, east and west. The darkness wouldn’t claim her.

And of course, Po would never have sent her into this cave if it were a place she could not endure. Her shoulder hit rock, and she heard a muffled slap that sounded like surface water on shore. She kicked forward toward the sound, and then her head burst above water, and she was breathing. She felt around and found the rock whose underside she’d struck. It jutted above the surface and felt flat and mossy on top. She pulled herself onto it, teeth chattering.

It was blacker in this cave than any night she had ever known. There was not a flash on the water, not even a thinner blackness to give shape to the space around her. She stretched her arms but touched nothing. She had no sense of the height of the ceiling or the depth of these walls. She thought she heard water slapping against rock for some distance, but she couldn’t be sure without exploring. And she wouldn’t explore, because they hadn’t the time.

So this was Po’s cave. He would be safe enough here, if he could get himself here, for no one who didn’t share his Grace could ever find him in this cold, black hole under the mountain.