'Sir Thomas, sire... You need to get up.'

Sir Thomas Kartzela woke, his dreams dispersing like smoke. It was early, and the grey morning light leaked into his bed chamber through the narrow east window. Somewhere a bell was clanging, an ugly, urgent sound.

The great black key that hung from his neck was cold against his skin. He touched it with his left hand, reflexively, as he did whenever he woke.

At the far south of the principality of Kuek, over the chasm and thundering river that formed its southern-most border, was a stone bridge. It was built three hundred years ago, by hands unknown, and it spanned the gulf, far above the raging water. It was wide enough for three knights to ride abreast, although it had no walls to prevent a rider from falling; and it was held up by pillars that seemed impossible, but nevertheless still supported its moss-covered bulk.

'Sire, out there. There's something you need to see...'

Someone was outside, calling through his door. The bell kept up its relentless noise.

The old knight pushed the blankets away and sat up in his bed. He swung his legs out, and his bare feet met the smooth wooden floor.

The north end of the bridge had a gatehouse. It as old as the bridge; and it too was made of smooth stone blocks, their joins almost invisible. The gate itself was wood, heavy solemn oak, a pair of huge doors studded with metal.

The south end of the bridge had no buildings, and beyond it was a track that petered away into scrubby moorland. The mists hid whatever was beyond, and humanity did not go there. It was the edge of the world, and this bridge was the sole place that you could reach it.

Sit Thomas pulled on tunic and boots, the key still next to his skin. He picked up his sword belt, and his right hand closed around the hilt, like it always did. Then he strapped the belt around his waist, threw his black cloak over his shoulders, and opened the door to his room.

His family had ruled these lands for as long as they had held records. The legend went that, before their fall, the first King had gifted this gatehouse to his most loyal knight, and told him to keep watch. If that was true, it was a meagre gift: out here, where the rain streaked from the grey sky, and the purple flowers bobbed in the brutal cold south winds, humanity didn't thrive, they clung to the land. The Kartzela family motto was simple: 'endure'. And that was what they had done, generation upon generation, their little family castle not much larger than the tumbledown huts of the serfs who scraped along beside them. Even the Kings had fallen, usurped by warring princes; but the bridge, the gatehouse, and the Kartzelas remained.

'Sire, you need to come to the gatehouse,' said the man who'd been calling him.

It was Gwynn, the youngest of his garrison of four. He was barely an adult, his beard not much more than fluff. He was nervous, his eyes darting around like minnows, beads of sweat on his forehead even in the cold morning air.

Sir Thomas nodded. 'Show me.'

They set off down the stairs, down to the stables, lighting their way with tallow candles that flickered in the draughts.

Sir Thomas was the last of his line. His mother had died bringing him into the world, and it had broken his father, who had passed away a mere decade later. It had been his family's custom to send the eldest son to the city of Hallen, to find a wife, a minor noblewoman who would thrive in the wild loneliness of the south, so that the family could continue and they could endure; but James had been the only surviving child and he had taken up his father's spurs at ten and had no time or ability to travel. And now here he was, at fifty six, as grey and seamed as the stone that he ruled over, riding to the ancient gatehouse that was his heritage.

'I came to get you straight away, sire. I rang the bell and woke the others. I don't know what it is...'

The boy was babbling, riding alongside.

'Hush, Gwynn,' said the knight. He wanted his mind clear of the chatter.

The rolling morning mists were dispersing in the weak sun, exposing earth and stone and grass. Ahead of them the bell clanged with dull urgency, and then stopped, the last stroke muffled in the cold, damp air.

'Hail Sir Thomas,' shouted Roderick from the gatehouse. His sword was out, held up in salute.

'Hail Roderick,' replied Sir Thomas. He rode up to where the man was standing, so that he could speak without raising his voice. 'What's the reason for the alarm?'

Roderick was nearly as old as the knight, and had served him since childhood. The two of them had grown old together, and Sir Thomas trusted the man with his life.

'We have a visitor, sire,' replied Roderick.

'On the bridge?'

'Yes sire. He's standing at the centre.'

Sir Thomas nodded, his grey eyes on the door. 'Thank you, Roderick. Gwynn, ride to the guard tower at Helleth, as hard and fast as you can. Let them know. Go. Go!' As soon as the boy had left, he turned to Roderick. 'I want my lance, cuirass, and shield. Prepare to open the gates.'

Roderick shouted to the other two men to get the knight's armour. They blinked and then did as they were told, still stupefied from being recently woken by the bell.

Sir Thomas's family crest was a sable sword and key, crossed, over a grey background. This was painted on his shield, the black symbols huge on the heavy wood. His armour was simple and tough, designed for war, not show. He had drilled in it every day for his entire life, and it felt like a second skin. It was oiled and cold, the same grey as the sky, the same grey as his shield. He threw his black wool cloak over his shoulders, and took the key from round his neck, and passed it to Roderick, and then remounted his horse. Roderick handed him a lance, as unadorned and brutal as everything else he owned. The men ran to the lock, and pulled the huge doors open, grunting with the strain.

Sir Thomas Kartzela rode a few steps onto the bridge, lance lowered, hood down against the light rain. There was indeed a visitor, standing at the centre of the bridge.

Roderick's men pushed the gate closed behind him, and locked it, as they had practised together endlessly.

'Hail, stranger,' shouted the knight. 'What's your business here?'

The stranger looked like he'd been carved from a kinder sky. His cloak was the pure blue of a summer morning, edged with the gold of sunrise. His skin was the ultramarine of a clear, autumn evening. His sword was the orange of the clouds at sunset. His hair was black, and twinkled with tiny silver stars. He stood, on foot, alone, his sword sheathed.

'Hail, sir gatekeeper,' replied the stranger. 'My name's Khate. I've got a message for your King.'

His voice was low, and clear.

'There are no more Kings,' replied Sir Thomas. 'This land's called Kuek, and it's ruled by my Prince. What do you want to tell him?'

The stranger, Khate, nodded. 'I understand – a lot has changed. Then send this message to your Prince, and he can decide what to do with it. The message is this: "the jailer is nearly ended, and you will be free." Goodbye, Sir Thomas Kartzela.'

He bowed, and turned, and walked back, across the bridge, out into the mists at the edge of the world.

When he had disappeared, Sir Thomas turned, and rode back through the gate.