But even his newfound happiness could not curb Barry's restless tension. Large as it was, the cavern of Tana was still confining to one accustomed to the open sweeps of Earth, and the threat of Komso hung like a looming storm cloud. And, despite much thinking and long, fruitless conversations, neither Barry nor Xintel could see a way to attack the Chosen's almost invulnerable position.
Roaming the great cave, Barry's attention turned one day to the gas filling the upper portion. It gathered from the tiny bubbles given off by the submarine plants, with even the living houses of Tana contributing, and its level was nearly constant. Whenever its volume increased beyond a certain point the excess spilled into the tunnel leading to the open sea.
"What's up there?" he asked.
Xintel laughed. "It should do no harm to go there."
Together they swam high above the town along one insloping wall of the cavern, passing through the thin layer where swarming microscopic life furnished Tana's constant illumination, and reached the surface.
"Clear the water from your lungs all at once," Xintel instructed him. "It's easier that way."
She exhaled as far as possible, water pouring from her open mouth, and gasped in a breath of gas. He did likewise, and after some choking and coughing, found he could breathe.
They climbed out on a slanting rock outcropping and he stared around.
"This gas must be almost pure oxygen," he said, his voice ringing hollowly.