The hissing approach spread across the night behind them. They turned their heads as they walked, saw the mound of the coursing worm.

"Keep moving," Paul whispered. "Don't look back."

A grating sound of fury exploded from the rock shadows they had left. It was a flailing avalanche of noise.

"Keep moving," Paul repeating.

He saw that they had reached an unmarked point where the two rock faces--the one ahead and the one behind--appeared equally remote.

And still behind them, that whipping, frenzied tearing of rocks dominated the night.

They moved on and on and on . . . Muscles reached a stage of mechanical aching that seemed to stretch out indefinitely, but Paul saw that the beckoning, escarpment ahead of them had climbed higher.

Jessica moved in a void of concentration, aware that the pressure of her will alone kept her walking. Dryness ached in her mouth, but the sounds behind drove away all hope of stopping for a sip from her stillsuit's catchpockets.

"Lump . . . lump . . . "

Renewed frenzy erupted from the distant cliff, drowning out the thumper.

Silence!

"Faster," Paul whispered.

She nodded, knowing he did not see the gesture, but needing the action to tell herself that it was necessary to demand even more from muscles that already were being taxed to their limits--the unnatural movement . . .

The rock face of safety ahead of them climbed into the stars, and Paul saw a plane of flat sand stretching out at the base. He stepped onto it, stumbled in his fatigue, righted himself with an involuntary out-thrusting of a foot.

Resonant booming shook the sand around them.

Paul lurched sideways two steps.

"Boom! Boom!"

"Drum sand!" Jessica hissed.

Paul recovered his balance. A sweeping glance took in the sand around them, the rock escarpment perhaps two hundred meters away.

Behind them, he heard a hissing--like the wind, like a riptide where there was no water.

"Run!" Jessica screamed. "Paul, run!"

They ran.

Drum sound boomed beneath their feet. Then they were out of it and into pea gravel. For a time, the running was a relief to muscles that ached from unfamiliar, rhythmless use. Here was action that could be understood. Here was rhythm. But sand and gravel dragged at their feet. And the hissing approach of the worm was storm sound that grew around them.

Jessica stumbled to her knees. All she could think of was the fatigue and the sound and the terror.

Paul dragged her up.

They ran on, hand in hand.

A thin pole jutted from the sand ahead of them. They passed it, saw another.

Jessica's mind failed to register on the poles until they were past.

There was another--wind-etched surface thrust up from a crack in rock.

Another.

Rock!

She felt it through her feet, the shock of unresisting surface, gained new strength from the firmer footing.

A deep crack stretched its vertical shadow upward into the cliff ahead of them. They sprinted for it, crowded into the narrow hole.

Behind them, the sound of the worm's passage stopped.

Jessica and Paul turned, peered out onto the desert.

Where the dunes began, perhaps fifty meters away at the foot of a rock beach, a silver-gray curve broached from the desert, sending rivers of sand and dust cascading all around. It lifted higher, resolved into a giant, questing mouth. It was a round, black hole with edges glistening in the moonlight.

The mouth snaked toward the narrow crack where Paul and Jessica huddled.

Cinnamon yelled in their nostrils. Moonlight flashed from crystal teeth.

Back and forth the great mouth wove.

Paul stilled his breathing.

Jessica crouched staring.

It took intense concentration of her Bene Gesserit training to put down the primal terrors, subduing a race-memory fear that threatened to fill her mind.

Paul felt a kind of elation. In some recent instant, he had crossed a time barrier into more unknown territory. He could sense the darkness ahead, nothing revealed to his inner eye. It was as though some step he had taken had plunged him into a well . . . or into the trough of a wave where the future was invisible. The landscape had undergone a profound shifting.

Instead of frightening him, the sensation of time-darkness forced a hyper-acceleration of his other senses. He found himself registering every available aspect of the thing that lifted from the sand there seeking him. Its mouth was some eighty meters in diameter . . . crystal teeth with the curved shape of crysknives glinting around the rim . . . the bellows breath of cinnamon, subtle aldehydes . . . acids . . .

The worm blotted out the moonlight as it brushed the rocks above them. A shower of small stones and sand cascaded into the narrow hiding place.

Paul crowded his mother farther back.

Cinnamon!

The smell of it flooded across him.

What has the worm to do with the spice, melange? he asked himself. And he remembered Liet-Kynes betraying a veiled reference to some association between worm and spice.

"Barrrroooom!"