out into the open water. On a rock nearby, a hunched, gnome-like figure was crouched. Then I saw his face, goggled with great round eyepanes and nose-breather, with a pipe that led to a pack on his back.

Nereid steered us toward him; we stopped and I reached and seized him.

"You did this?" I demanded. "You turned loose the gas that killed these people? Who told you to do it? Who gave you the gas, and the mechanisms to spread it?"

His laughter turned to a terrified whimpering. Nereid murmured,

"That mask he's wearing—the workers use that, in our agriculture when they spray with the nitro-carbon. But we have no sprayers that could do a thing like this, nor gas deadly enough."

"You did it?" I shook him.

And then he was laughing again. And suddenly I realized that of course he could not understand English. I cast him loose. And Nereid flung questions at him in her own language.

"Figures came up from the water," she said. "He happened to have his mask and saved himself."

We left him there on the rock, still laughing. Tollgamo's first attack! Would he try to loose this gas on Arron? Our little boat sped past the Water City. I could see now that the quivering, slithering vegetation everywhere was engulfing the flimsy houses. Its stimulated growth would persist, an hour or a day, and then subside.

Shuddering, we drove our boat onward. The great Arsenal rock loomed ahead of us now, a huge almost square lump of metallic rock rising sheer from the water to a height of two or three hundred feet. On all sides it was like that; its only access was from beneath where subterranean passages ran into its honeycombed, grotto interior. Impregnable fortress, save from beneath the sea.

Nereid tied our little craft to a metal fastener against the black, sleek rock-cliff. Then for me she produced the air-mechanisms and round transparent helmet with elastic gasket to fit around my throat. And heavy, metal-weighted shoes for us both.

But no helmet was needed for her. "We will be there in ten or fifteen minutes," she said. "I can see better without the head-covering."

We dropped into the luminous, opalescent water. Nereid held my hand as I floundered a little, trying to remain balanced upright while our weighted 

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