The howls of the storm through the window hole were the only sounds in the den as Zeus padded to the center of the circle. Some wild dogs licked their jowls and panted. The few who had cowered under Shep’s gaze now looked up at him, their eyes black slits, their tails flicking.

Zeus’s head hung low and there was no wag in his tail. There was a gash in the fur on his shoulder.

“Please, no,” Shep whimpered, the noise escaping his muzzle before he could think better of it.

Zeus’s ears pricked up immediately. Every hair on his body trembled at this expression of weakness. “What?” he growled. “Do you yield?” He stepped one paw closer to Shep, his jowls trembling.

Shep regained his stance — chest out, ears alert, tail up. “I do not yield,” he spat.

Shep’s heart pounded inside his chest. He could not abandon the other dogs to these mongrels. But to have to fight Zeus to protect them? Kill his best friend?

Not wanting the wild pack to see his teeth chatter, Shep locked his jaws. He had to stay strong. Everything could change in a heartbeat and the entire pack would be on him.

Zeus moved a stretch closer to Shep. The whole world was reduced to that space of stone: two dogs, best friends. And only one could step out of that circle.

Shep sniffed his friend. “They attacked you?”

Zeus licked his nose. “It’s their way,” he growled. He began to circle Shep.

Shep shuffled on his paws, following Zeus’s movements, always maintaining his stance. “You could have just walked away,” Shep woofed. “Why challenge me?”

“How better to prove to the wild dogs I’m as good as they are?” Zeus spat a hard pant. “And why should you get to lead?”

“This can’t be the life you want.” Shep could still see a glimmer of the old Zeus in his friend’s eyes. “Join me. We might have a chance,” he snuffled quietly. “Together, we could get out of this.”

It seemed that, for a heartbeat, Zeus considered Shep’s offer. He looked around at the snarling crowd of dogs, his ears up, his tail lifted. Then he snorted loudly and bared his fangs. “I don’t want to get out of this,” he growled. “I want to be wild.” Zeus crouched, hackles raised. “Good-bye, friend.”

Shep braced his paws. “Good-bye,” he woofed.

They met in midair, claws raking fur, fangs scraping jowls. Shep and Zeus had played together for long enough that they knew each other’s moves before they thought them. Their claws reacted almost instinctively, meeting a flank as it whirled through the air, catching a jowl as it flapped over an open jaw. Shep would snap not at where Zeus’s neck was, but where he knew it would be in two heartbeats.

The wild dogs bayed with excitement. They leapt on one another’s backs and panted with anticipation as they watched the two masterful fighters.

Shep and Zeus separated after each entanglement of claws, pausing for mere heartbeats to catch their breath or to spit slobber. Then they sprang off trembling hind legs, claws extended and fangs bared. First Zeus had the upper hold and flung Shep to the floor. Then Shep attacked from below and dragged Zeus over, throwing him onto the stone.

Once again, Shep felt the sickening excitement of the fight cage. Once again, he tasted lifeblood, and it tasted good. He felt the darkness taking over. And this time, he knew it was the Black Dog. It was like the tails of dawn wagging in his mind. The Black Dog was not outside of him; it was inside, like a sickness. Winning this fight would not make him the Great Wolf; winning here would make him the Black Dog. Shep realized that that had always been his fear — all those nightmares, they all came down to this: That it was not the Great Wolf, but rather the Black Dog who ruled him.

Shep pulled away from Zeus and slid across the floor, nearly careening into the circle of wild dogs.

“We don’t have to do this!” Shep bellowed. “There’s another way!” Perhaps some of the dogs would listen to his bark.

Zeus’s eyes were wild — the whites exposed and riddled with red lines. His hackles bristled along his spine. “I’ve never seen you give up,” he spat.

“Why are we fighting?” Shep cried, turning to the nearest dogs. “There’s enough in this den for us all!” He smelled their confusion — they looked at one another, and some whimpered. There was hope yet!

Zeus turned to the largest group of dogs. “The pet forfeits!” he howled, fangs bared. “The den is ours!”

“We’re all dogs!” Shep screamed. “We’re one pack!”

The wild dogs were too far gone; the Black Dog had their pack by the scruff. They began to close in. Shep felt a claw rake his chest, a fang clip his tail. He hoped Callie had found an escape, another secret back door.

A strange roar crackled Outside. All the dogs pricked their ears at the noise. Shep realized that he wasn’t the only dog who’d never heard such a sound before. It was like the rush of water from the paw in the Bath, only bigger, louder. The air suddenly smelled of the beach — salt and wet and endless blue.

And then Shep saw it.

A wall of water. In it floated whole trees, Cars, bits and pieces of the entire world.

It was coming straight for them.