Ballard's traveling at nearly full throttle. The lamps on her helmet and squid stab the water like twin lighthouse beacons. Clarke, her own lights doused, catches up about halfway to their destination. They cruise along a couple of meters over the muddy substrate.

"Your lights," Ballard says.

"We don't need them. Sonar works in the dark."

"Are you breaking regs for the sheer thrill of it, now?"

"The fish down here, they key on things that glow—"

"Turn your lights on. That's an order."

Clarke doesn't answer. She watches the beams beside her, Ballard's squid shining steady and unwavering, Ballard's headlamp slicing the water in erratic arcs as she moves her head—

"I told you," Ballard says, "turn your—Christ!"

It was just a glimpse, caught for a moment in the sweep of Ballard's headlight. She jerks her head around and it slides back out of sight. Then it looms up in the squid's beam, huge and terrible.

The abyss is grinning at them, teeth bared.

A mouth stretches across the width of the beam, extends into darkness on either side. It is crammed with conical teeth the size of human hands, and they do not look the least bit fragile.

Ballard makes a strangled sound and dives into the mud. The benthic ooze boils up around her in a seething cloud; she disappears in a torrent of planktonic corpses.

Lenie Clarke stops and waits, unmoving. She stares transfixed at that threatening smile. Her whole body feels electrified, she's never been so explicitly aware of herself. Every nerve fires and freezes at the same time. She is terrified.

But she's also, somehow, completely in control of herself. She reflects on this paradox as Ballard's abandoned squid slows and stops itself, scant meters from that endless row of teeth. She wonders at her own analytical clarity as the third squid, with its burden of sensors, decelerates past and takes up position beside Ballard's.

There in the light, the grin does not change.

Clarke raises her sonar pistol and fires. We're here, she realizes, checking the readout. That's the outcropping.

She swims closer. The smile hangs there, enigmatic and enticing. Now she can see bits of bone at the roots of the teeth, and tatters of decomposed flesh trailing from the gums.

She turns and backtracks. The cloud on the seabed is starting to settle.

"Ballard," she says in her synthetic voice.

Nobody answers.

Clarke reaches down through the mud, feeling blind, until she touches something warm and trembling.

The seabed explodes in her face.

Ballard erupts from the substrate, trailing a muddy comet's tail. Her hand rises from that sudden cloud, clasped around something glinting in the transient light. Clarke sees the knife, twists almost too late; the blade glances off her 'skin, igniting nerves along her ribcage. Ballard lashes out again. This time Clarke catches the knife-hand as it shoots past, twists it, pushes. Ballard tumbles away.

"It's me!" Clarke shouts; the vocoder turns her voice into a tinny vibrato.

Ballard rises up again, white eyes unseeing, knife still in hand.