"Hard going, Keith. God—the cavern's right ahead!"

It was ghostly to hear Hemmy's warm voice from the lifeless solitude outside. Breath coming quickly, Wells watched the silent scene—the cleft in the wall of rock overshadowing everything now. The diver fought ahead, gaining inch by inch.

Now, save for occasional clumps of weed, he was exposed to the enemy.... Now the last desperate gauntlet was reached.... Keith felt his blood pound hotly.

"I'm gaining, Keith. Gaining...."

Bowman had little breath for speech. His tiny form battled on, now sinking from sight as he dropped into some masked gully, now wrestling slowly with great swaying strands of kelp, but always struggling ahead.

"I'm at the bow, Keith! The hawser arm's right in our mooring holes. I'll go halfway before fastening the charge. Any signs of life from the devil?"

"None yet, Hemmy. But go slow. Hide all you can, old man, for God's sake!..."

Right beneath the metal arm, Bowman's dwarfed figure crept doggedly ahead. Forward, inch by breathless inch. Kelp thickened, washed away; the two hulking submersibles, captor and captive, surged onward—but just a little faster went the valiant figure with the black charge on its back.

The towing monster had its snout in the cavern. The darkness thickened. Bowman was quarter way!

He plunged desperately. Half way!