The tunnel went on and on and there was no more mindless, silly chatter. This was business now. It took them another fifteen minutes to get through the tunnel and this opened into an immense elliptical antechamber that was something like a thousand feet in circumference at its widest point, sonar told them. Their halogens only penetrated maybe fifteen feet into the clotted murk. It was like moving through a sandstorm at times. From far below, a colony of tubeworms were a forest of pale, rubbery stalks. There had to be hundreds if not thousands of them.

“Like a sea of arteries,” Murphy said.

The tubeworms were hollow, about as big around as baseball bats, swaying from side to side. They grew up from twenty feet below and rose fifteen feet above their heads.

“Don’t get lost in there,” Javonivic said.

They were proceeding by sonar alone now. On the other side of the chamber there was a large oval passage and beyond that, somewhere, the anomaly itself. Using the suit jets, they plowed through the tubeworms, disturbing the rumination of vent fish and pulsing eyeless mollusks much like cuttlefish.

The passage.

Although there was no real reason—other than the usual ones—to fear it, as their lights played over it, Bell was seized by a cold, enveloping dread like it was the mouth of a cave leading to the lair of some flesh-eating beast. Both he and Murphy paused just outside of it, hanging there in the sediment. In the lights of Murphy’s helmet, Bell could see that he was feeling the same thing.

“All right, girls,” Orr said. “What’s the hold up?”

“Nothing, sir,” Bell told him.

Working his footpad thrusters, he edged forward into the passage, Murphy at his side. The dread did not abate, but deepened. It felt like birds were taking wing in his belly. His breath was coming fast now, his heart pounding. He knew that Orr and Javonivic were picking up his agitated vital signs.

“Take it easy,” she said. “Just take it easy.”

They pushed through the passage. The walls were clustered with colonies of round sponges and pink wavering anemone tentacles. They passed giant clams and looping mud worms, punched through dense clouds of krill. The tiny shrimplike animals clung to the aluminum shells of the hardsuits, wiggling their feathery legs.

The further they went, the less life there was until there was none at all. Not even a stray crab skeleton in the collected sediment below. Just that passage, dark and smooth-walled, leading on and on.

“You gotta be damn close now,” Javonivic said.

They said nothing. Deeper and deeper they went. The passage was narrowing steadily, but was still quite large.

“Hell is that?” Murphy said, stopping.

Bell was seeing it, too.

Coming from farther down the passage was a phosphorescent glow that was lighting up the tunnel. And whatever was making it, it was coming straight at them.