1. The Missing Acorns

A long time ago, when humans still lived in cities, on a cold morning near the end of a long, cruel winter, in magnificent Central Park in the middle of magnificent New York City, a young squirrel named Patch was awakened very early by the growls of his empty stomach.

A squirrel's home is called a drey. Patch's drey was very comfortable. He lived high up an old oak tree, in a hollowed-out stump of a big branch that had long ago been cut off by humans. The entrance was only just big enough for Patch to squeeze in and out, but the drey itself was spacious, for a squirrel. Patch had lined his drey with dry leaves, grasses and bits of newspaper. It was warm and dry, and on that cold morning he would have liked nothing better than to stay home all day and sleep.

But he was so hungry. Hunger filled him like water fills a glass. The cherry and maple trees had not yet started to bud; flowers had not yet begun to grow; the juicy grubs and bugs of spring had not yet emerged; and it had been two days since Patch had found a nut. Imagine how hungry you would feel if you went two whole days without eating, and you may have some idea how Patch felt that morning.

Patch poked his head out of the drey into the cold air and shivered as he looked around. Clumps of white, crumbly ice still clung to the ground. Gusts of cold wind shook and rustled the trees' bare branches. The pale and distant sun seemed drained of heat. Patch took a moment to satisfy himself that there were no dangers nearby, no hawk circling above or unleashed dog below. Then he emerged from his drey and began to look for acorns.

But what marvels, what miracles, what mysteries are hidden inside those simple words!

Squirrels are extraordinary creatures. Think first of how they climb. When Patch left his drey, he went up, not down. He passed the drey of his friend and neighbour Twitch, climbed to the northernmost tip of his oak tree's cloud of barren branches, and casually hopped onto the adjacent maple tree, home to his brother Tuft. To a squirrel, every tree is an apartment building, connected not only by the grassy thoroughfares of the ground but by sky-roads of overlapping branches. Tree trunks are like highways to them, even branches thin as twine are like walking paths, and they leap through the sky from one tree to another like circus acrobats.

When he reached the last of the thick grove of trees, Patch paused a moment to look around and consult his memory. His memory was not like yours or mine. Human memories are like messages written on crumbling sand, seen through warped glass. But squirrels have memories like photograph albums; exact and perfect recollections of individual moments. Patch, like every squirrel, had spent the past autumn burying hundreds and hundreds of nuts and acorns, each one in a different place. And he had stored all of those places in his memory book. The winter had been long, but Patch's memory book still contained a precious few pages that depicted the locations of nuts buried in the autumn, but not yet dug up and eaten. Patch climbed to a high branch, stood on his hind legs, and looked all around, seeking an image from one of those memories.

If you had looked at Central Park that morning with human eyes, you would have seen concrete paths, steel fences, a few early-morning joggers and dog walkers, all surrounded by fields of grass and ice and bare trees and rocks, and beyond them, Manhattan's endless rows of skyscrapers.

But with Patch's eyes, with animal eyes, he saw no park at all. Instead he saw a city in itself. A vast and mighty city called the Center Kingdom. A city of trees, bushes, meadows and lakes; a city scarred by strips of barren concrete; a city surrounded by endless towering mountains. All manner of creatures lived in this city. Squirrels in their dreys, rats and mice in their underground warrens, raccoons in the bushes, fish and turtles in the lakes, birds fluttering through the trees or resting in their nests. At that hour on that day, very early on a winter morning, the Center Kingdom was almost abandoned – but soon spring would come, and the city would bloom into a thriving maelstrom of life and activity. All Patch needed to do, until that blessed time arrived, was find enough food for these last few days of winter.

He saw in the distance, near the edge of the densely wooded area he called home, a jagged rock outcropping from his memory book. He was so hungry he paused only a moment to check for dangers before racing headfirst down the tree trunk and towards the rocks. In his memory that same outcropping was just there – and the nearest human mountain visible over the treetops to the west was there – and a particular maple tree, which had been covered in orange and scarlet leaves on the day Patch buried the acorn, had been exactly there, and that far away.

Patch found his way to the exact spot where all those landmarks fell into place, so that the place where he stood and the page from his memory book matched perfectly, like a picture and its tracing. Then he began to sniff. He knew as an undeniable fact that in the autumn he had buried an acorn within a tail-length of where he stood. And squirrels can smell perfume in a hurricane, or a dog a half-mile upwind, or a long-buried acorn.

But Patch smelled nothing but grass, and earth, and normal air-smells.

His heart fell. It seemed to fall all the way into his paws and seep out through the tips of his claws. Patch let out a little murmur of awful disappointment. There was no food here. This acorn was gone, already gone.

This was not unusual. Squirrels often found and ate nuts buried by other squirrels. But the same thing had happened with every nut Patch had tried to unearth for the last two days. And that was unusual. It was such an astonishing run of bad luck that Patch had never heard of such a thing happening before.

He dug anyway, hoping that maybe this acorn had no smell, or his nose was not working right. But he found nothing. And when he found the next burial place, again there was nothing. He ran to the next; and the next; until finally there were no more pictures left in Patch's book of memories, no nuts left to try to unearth. And he was so hungry.

By this time other squirrels too had emerged from their dreys and were digging for food. Patch knew all of the half-dozen squirrels he could see around him, and the dozen more whose presence he could smell in the cold wind. They were all of his tribe.

Squirrels are social animals, they have family and friends, clans and tribes and kingdoms. Patch's tribe, the squirrels of the Treetops, were not like the Meadow tribe who lived near the city's grassy plains, or the Ramble tribe that inhabited its rockiest wilderness, or the red Northern tribe. The Treetops tribe was more a group of individuals than a community. If they had had a motto, it would have been, "Take care of yourself." None of the squirrels around Patch were of his clan. It would have been a terribly low and shameful thing for Patch to go to one of them and ask for even a single bite of an acorn. But while pride is important, it cannot be eaten, and hunger is more important still. Patch was so hungry he would have begged for food.

But there was no one to beg from. For not a single one of the squirrels around him had found a nut this morning. All of them had been digging for nothing.

Patch sat and thought.

He was, you must remember, a squirrel, an animal, a creature of instinct. Thinking did not come naturally to him. He had to sit for a long time while he thought, in a little fenced-in patch of grass near to one of the concrete-wasteland human trails. Around him there was little to see. In winter most birds flew south, rats stayed underground, raccoons hibernated. There were only the other hungry squirrels, a few fluttering pigeons, and the occasional passing human.

At one point an unleashed dog came near, and Patch had to interrupt his thinking to watch this threat. It was a very strange dog. If it was indeed a dog at all. It looked like a dog, but it was unaccompanied by any human, and it had a rich, feral scent like that of no other dog Patch had ever encountered. The dog-thing said nothing, which was also unusual, but it watched Patch with a leery grin full of sharp teeth for what felt like a long time. Patch was very glad of the fence that surrounded him. When the dog-thing finally moved on Patch sighed with relief. He could have escaped to the safety of a nearby tree if necessary. But he was so hungry that the effort of running away, combined with the terrible strain of thinking, would have left him weak and dizzy.

By the time Patch finally finished thinking, he had drawn one conclusion and made two decisions.

The conclusion was that something was very strange and wrong. It was not Patch alone who had lost all of his food. That would have been bad enough. But the same thing seemed to have happened to every member of his tribe. That could not be mere ill-luck. Something more, something worse, was happening. There were dark stories told in whispers among squirrels, ancient legends of winters that had outlasted all the Center Kingdom's buried nuts, famines in which nine in every ten squirrels had died of hunger, and the few survivors had been forced to eat the bodies of the dead in order to live. But there were no legends in which all buried acorns had vanished uneaten from the earth. This was something new.

The first decision he made was that he would seek out his family, and see if they had any food. Patch was solitary by nature, and had not seen his family or indeed spoken to any other squirrel for three days, but he knew they would help him if they could, just as he would help them.

His second decision was that if his family did not have food, then … he would try something else. Something very unusual, for a squirrel. Something very daring and dangerous. But by this time hunger was growing stronger in Patch than fear.