Starting out, he’d hesitated between every move, testing and retesting each hold, but no more. Already, his legs had begun to sporadically tighten—a precursor to cramps. If he was hit with one up here on the wall that might very well be the end.

And so he climbed as fast as he could, taking every decent hold he encountered, trying to find comfort in the growing distance between himself and the floor of the canyon, assuring himself that should he fall, it would be far better to just die right off, because a broken leg or back out in this barren wilderness would only mean a slow and agonizing death.

And yet the higher he climbed, the terror gripped him tighter, Ethan fighting the urge to look down, but he couldn’t resist the morbid fascination with how far he was taking himself above the ground.

His right hand finally reached the third ledge.

He strained to haul himself up, digging his left knee into the edge.

By the time he realized there was nothing obvious for his left hand to grasp, he was already committed.

There was an endless second where Ethan hung in midair, one knee perched on the ledge as his center of gravity slowly dragged him back from the wall toward that terrible emptiness beneath him.

He lunged out in total desperation, both hands clawing at the rock, his left just managing to find a crimp at chest level.

For a moment, he didn’t know if he had a sufficient grip to reverse gravity’s undertow and pull himself back onto the ledge, the surface of his fingertips scraping away, his knuckles blanching from the strain.

His backward momentum stopped, and he tugged himself forward by the tips of his fingers until his forehead grazed the wall.

Took everything in his power to swing his right leg up and make himself stand.

This ledge was half the width of the last one and his feet hung off the edge.

Would’ve been impossible to sit down or to remain here for any extended length of time.

The crack in the wall that climbed the remaining distance to that piece of metal opened up just above him. Looked wide enough for Ethan to squeeze into if he could get there, but he didn’t have the strength to try to pull himself up just yet.

He’d nearly died, and his body, head to toe, was still shaking.

The scream ripped him out of his own fear.

He stared fifty feet down to the canyon floor, baffled.

He’d crushed that thing’s skull into pieces.

How the hell—

Wait.

It wasn’t moving, and it no longer had a mouth to even produce such a noise.

As the next scream—this one a shade lower in pitch—resounded through the canyon, bouncing back and forth between the walls, Ethan looked back toward the electrified fence.

Oh God.

There were five of them moving up-canyon in a pattern that almost resembled a squadron formation, ascending that field of large boulders in fast, elegant leaps.

Ethan pressed his back against the wall, trying to establish as steady a perch as he could find.

The pack leader came sprinting out of the boulder field at full speed, as fast as a dog, and when it reached what Ethan had killed, it skidded to a stop and lowered its head to the ground, sniffing the smashed skull of its compatriot.

As the others closed in, it raised its face to the sky and cut loose a long, brokenhearted moan that resembled the howl of a wolf.

The other four arrived and within ten seconds they were all howling like a choir in mourning, Ethan growing cold as he stood motionless on the ledge listening, his sweat cooling on his skin and the remnants of blood from that thing drying on his face like tiny scabs.

He tried to comprehend what he was seeing and hearing, but there was no explanation.

It was all utterly beyond his experience, and possibly his imagination.

When the howling ended, the group turned to one another and conversed in the strangest language Ethan had ever heard.

Like dreadful birds—an eerie chirping quality to their fast, sharp squawks.

Ethan tightened his grip on the rock, fighting against a wave of dizziness, the world tilting beneath him.

All five of them were sniffing the ground now in the vicinity of the dead one—haunches high, faces jammed down between the rocks.

Ethan tried not to panic as it hit him, but he realized something standing there above the monsters—after they left, there was no way he could climb back down. Not even off this ledge. The only way off this wall, where he’d so thoroughly bitten off more than he could chew, was up.

One of the creatures suddenly barked a high, piercing shriek.

The others rushed over, gathering around and chirping frantically, and then the largest of the bunch—easily twice the size of the one that had attacked Ethan—broke out ahead of the others, its nose still to the ground.

Only as it reached the base of the cliff did Ethan finally understand.

My trail.

The creature pressed its nose into the rock and then came up on its legs.

It backed slowly away...

...and looked up, straight at Ethan.

They’re following my trail.

The canyon fell silent.

Five sets of milky eyes studying Ethan up on the ledge.

He could hear his heart raging in his chest like someone trying to beat a way out of a padded room.

A single thought scrolling through his mind on an endless loop...

Can they climb?

As if in answer, the large one who’d first picked up his trail reared back on its hind legs and sprang off the ground in a five-foot jump from a stationary position.

Stuck to the wall as if covered in Velcro, the points of its talons digging into tiny crevices in the rock that Ethan could never have used.

It gazed up the cliff face at Ethan as the others began leaping onto the wall.

Ethan looked up at the crack above his head, searching until he spotted a workable handhold just out of reach.

He jumped, palming a cluster of sharp, dark crystals as he heard the click of talons on rock ascending toward him.

He scrambled up the wall, got his other hand on a level surface inside the crack, and pulled himself the rest of the way into the opening of the chute.

It was tight, less than three feet across, but he forced his boots into the walls and created just enough opposing pressure to keep himself suspended.

He stared down.

The big one had already reached the second ledge, climbing fast, fearless, with no sign of fatigue.

The others close behind.

Ethan turned his attention to what lay above—a chute enclosed on three sides. Not much in the way of handholds, but he figured he could chimney up.