He felt tired. His old wounds were bothering him, as they always did when the weather was bad. The little he’d eaten at the previous station wasn’t enough to keep him going. He tied the horse’s reins to a post and went to find the station attendant, who turned out to be busy playing dice with the innkeeper.

He showed the attendant his credentials and watched the man’s embarrassment at being caught neglecting his duty. But Publius Sextius waved off his anxiety.

‘I’m not an inspector. I’m a simple traveller and I need your advice.’

‘Whatever I can help you with, centurion.’

‘I’m in a hurry, but I don’t know whether to continue on or stop for the night.’

‘I suggest,’ replied the attendant, ‘that you stop and rest. You’re not looking too good and in a short while it will be pitch black out there. Don’t risk it.’

‘How far is the next rest stop?’ asked Publius Sextius.

‘A little over three hours from here. It depends how fast you’re going.’

‘That depends on the horse you give me.’

‘So you want to leave?’

‘That’s right. It won’t be completely dark for at least an hour. Then I’ll see. Before I go I’ll have a hunk of bread and a little of whatever you’ve got. Change my horse. He’s outside tied to a post. Give me the best you have and I’ll remember you.’

‘Of course,’ said the attendant promptly, dropping his dice. ‘This is our innkeeper. He’ll serve you some dinner while I prepare the finest horse in the stables. Why are you in such a hurry, if I may ask?’

‘No, you may not,’ replied Publius Sextius curtly. ‘Get moving instead.’

The attendant did as he was told and the centurion soon set off again. The temperature was falling rapidly because of the snow still covering great swathes of the mountainside, frosting the air as it swept down the icy gullies.

Publius Sextius told himself that he was worrying too much, that there was no reason to think anything was about to happen so soon. But it relieved him to know that other couriers were already on their way, making it much more probable that the message would reach its destination.

He hoped the couriers would be equal to the task. The state had been lacerated by rival factions for too long now; even the local administrations had been infiltrated by men of different and conflicting loyalties.

Any lingering reflections of the sunset had been doused and the sky, clear now and deep blue, twinkled with its brightest stars. A crescent moon took shape over the white crests of the Apennines and the horseman felt even more alone on the deserted road, his only company the pounding of the horse’s hoofs and its heavy breathing.

Mutatio ad Medias, a.d. VIII Id. Mart., prima vigilia

The Medias changing station, 8 March, first guard shift, seven p.m.

As soon as darkness fell, while the others were preparing for dinner and lamps flickered on inside and outside the inn to guide in any latecomers, the man who had been unloading the sacks of wheat climbed the stairs that led to the upper balcony.

His move did not escape the grey-caped man. Under cover of the shadows that lined the portico, he stealthily reached the stairs and crept up behind him without making a sound, stopping at a door that the man had left half open.

The building was topped by a kind of tower that rose about twenty feet over the rest of the construction. Once the wrestler had reached the upstairs balcony, he walked over to this tower and used the steps built into the wall to reach its top. Out of sight now, he took wood from a readied stack and lit a fire inside a sort of cast-iron basket supported by a tripod. The wind soon whipped up the flames. The wrestler walked to a little door on the western side of the tower, opened it and retrieved a sackcloth bundle. Inside was a large, polished bronze disc. He used this to project the light of the fire towards a point high on the Apennines where someone was hopefully waiting for his signal and would understand. He made wide gestures with his arms, alternating and repeating them. The air was becoming quite chilly and the wrestler felt his chest burning so close to the flames, while his back was freezing in the cold night that was getting blacker and blacker by the moment.

The clanking of dishes and drinking jugs wafted up from below, along with the good-natured bawling of the guests, but the man didn’t take his eyes off the white blanket of the mountain. Although it was surrounded by darkness, it emanated an immaculate glow all its own.

He finally made out a red spot that became bigger and bigger until it was a pulsing red globe. The signalman up on the summit had received his message and was responding.

Down below, the man in the grey cloak didn’t dare go up the tower stair: he had no desire to provoke a run-in with that animal. Even from the balcony, he could tell that the man was sending a signal, so he just flattened himself against the wall and waited for the reply.

In Monte Appennino, Lux Fidelis, a.d. VIII Id. Mart., prima vigilia

The Apennine Mountains, Faithful Light, 8 March, first guard shift, seven p.m.

The man at the signal station held a canvas screen that he raised and lowered over the fire, but the wind was picking up, making his task much more difficult. The terrace at the outpost was covered with icy snow and behind the building stretched a forest of fir trees that were bent under the weight of the recently fallen snow. A hatch suddenly opened in the floor and the station commander emerged, wrapped in a coarse woollen cloak with a fur-lined hood. He was an army officer, an engineer.

‘What are they sending?’ he asked.

The signalman leaned the tablet on which he’d written the message close to the light of the fire. ‘ “The Eagle is in danger. Warn Cassia VIII.” Do you know what that means? Do you know who the Eagle is, commander?’

‘I do know and it means trouble. Terrible trouble. How many men have we got?’

‘Three, including the one who just sent us the signal.’

‘The wrestler?’

‘Yes, him, plus the two we have here.’

‘The wrestler will be leaving as soon as possible, if he hasn’t left already. The other two will set off immediately from here. They’re used to travelling at night. I’ll talk to them myself.’

The light pulsing from the top of the Medias tower stopped. Transmission of the message was complete.

The commander went back down the steps, pulling the wooden hatch shut after him. Three oil lamps illuminated the passageway that led to a landing from which the living quarters of the staff on duty at the station could be accessed. The two young men inside were both about thirty. The first, clearly a local, had a Celtic build and features. He was tall, blond and brawny, with iridescent blue eyes and long, fine hair. The second was a Daunian, from Apulia in the south. He wasn’t nearly as tall, his hair was sleek and dark and his black eyes sparkled. The first was called Rufus, the second Vibius. They used a strange jargon when speaking to each other, a mix of Latin and dialect from their native lands. There was probably no one else in the world who could have understood them.

They were eating bread and walnuts when their commander walked in. Jumping to their feet they swallowed quickly. They could see from the scowl on his face that the situation was serious.

‘Orders to deliver a message of the highest priority,’ he began. ‘Naturally, you won’t be alone. You know the protocol. Relying on light signals at this time of year with this bad weather is madness. If they tried it, it must mean they’re trying everything. A good courier is always the safest way. The message is simple. Easy to memorize, even for a couple of chumps like yourselves. “The Eagle is in danger.”’