The Apennine Mountains, the Oak Tavern, 10 March, five p.m.

The man in the grey cloak arrived out of breath, his horse exhausted and wild-eyed in fright at the lightning and thunder so loud the whole mountain seemed to shake. An angry wind whistled through the bare branches of the old oak trees, each new blast tearing away the last remaining leaves and carrying them off in a spin to the bottom of the dark valley. The high snowy peaks were barely visible against the black sky.

He found himself in front of the inn unexpectedly, after a bend in the road, and had to yank at the reins to avoid crashing into the doorway, which was already bolted against the approaching storm and the dark night. Another flash lit up the figure of the rearing horse and its rider for a moment, casting their shadow on the ground that was already drinking in the first heavy drops of rain. The odour of wet dust saturated the air, mixed with the metallic scent of the lightning bolts searing the face of the sky.

The horseman jumped to the ground and pounded hard on the door, using the knocker and then the hilt of his sword. The great oak tree that gave the inn its name loomed at its side, its gnarled boughs reaching to the roof of the building.

A stable boy came to answer the door. He took the horse by his reins and covered him immediately with a blanket.

The man dressed in grey entered and pulled the door shut behind him, bolting it as if he were in his own home. He walked towards the tavern as the rain began to pour, instantly filling all the cracks in the stony courtyard.

The inside of the tavern was a smoky hole. Crookedly placed beams held up a low ceiling and a round hearth in the middle of the room shot fumes and sparks towards an opening in the roof from which the rain dripped in, sizzling on the embers. An old man with a long white beard and eyes veiled by cataracts, wooden spoon in hand, was mixing some concoction bubbling in the copper pot. The newcomer took off his soaked cape and placed it on the back of a chair near the fire.

‘There’s spelt-meal mush and red wine,’ coughed out the old man without turning.

‘I have no time to eat,’ replied the other. ‘I have to get to-’

‘Mustela, it’s you, isn’t it?’

‘You can’t see a damned thing, old man, but your ears are holding out.’

‘What do you want?’

‘I have to get to the House of the Cypresses as fast as I can. Matter of life or death.’

‘We’ve got a good horse for you, Mustela. Yours must be done in.’

‘Don’t make me waste time. You know another way to get there.’

‘The short cut.’

‘Not fast enough. Faster.’

‘It’ll cost you.’

‘How much?’

‘Two thousand.’

‘I have less than a third of that, but if you tell me how to get there fast, I’ll give you double what you’re asking as soon as this is over.’

‘Why such haste?’

‘Do you want the money or don’t you? I guarantee you’ll get the full four thousand.’

‘All right.’

Mustela reached over to his cloak and pulled out a bag. ‘Shall I dump them here or should we go into the back?’ he asked.

The old man left the spoon in the pot and led his guest to the larder, which was dimly lit by a smoky tallow-burning lamp. Mustela poured the contents of the bag on to the table: all silver coins, looking newly minted.

‘Count them. There are five hundred, more or less. I’ll keep as little as possible for myself, but let’s get moving, damn it!’

The old man returned to the room with the fireplace, followed by Mustela. He called the stable boy as his guest retrieved his cloak, which was no less drenched than before but a little warmer. They walked into the courtyard and were greeted by a thunderclap that seemed to announce the collapse of the heavenly vault above them.

‘You won’t need your horse,’ said the old man, ignoring the storm. ‘I’ll keep him here as part payment of what you still owe me.’

‘What do you need all that money for?’ grumbled Mustela between one roll of thunder and the next.

‘I like to touch it,’ answered the old man.

The servant led the way, holding his lantern high enough to light up a tortuous path full of rain-soaked dead leaves. The red light cast a bloody glow on the trunks and branches of the big oaks and twisted chestnuts. The old man moved with a sure step over the slippery ground, as if he knew its every bump and hollow. He gave the impression of moving onward with eyes closed, guided more by the hooked toes of his feet than by the dim haze of his vision.

They ended up in front of a rock covered with moss and tangled thorn bushes. The servant pushed away a creeping bramble with his hands and uncovered a crevice in the rock.

The two men entered.

They found themselves in a narrow underground tunnel ending in a rough stairway cut into the stone, worn by time and dripping water. They groped their way down with their hands on the walls, step after step. The stairs became steeper and more irregular, but the difficulty of their descent was offset now by a rope that had been threaded through holes made in the jutting rocks. From deep below they could hear the sound of rushing water and the tunnel soon widened into a sandy-bottomed cave crossed by an underground torrent that bubbled up ferociously between the bare rocks and big limestone boulders.

‘This leads to a tributary of the Arno,’ said the old man pointing to the coursing stream.

Mustela looked at him in shock.

‘Isn’t this what you wanted?’ asked the old man. ‘The secret way?’

‘How long?’ asked Mustela with terror in his gaze.

‘That depends on you.’

‘What are you saying? Isn’t there a boat?’

‘There will be when you surface. You’ll find it hidden among the willows on the left bank.’

Mustela couldn’t tear his eyes away from the water, which in the dim light of the lantern seemed as violent and threatening as the surging Styx. The old man’s sunken, wrinkled face, framed by a stringy beard, was Charon’s.

He looked back at the water foaming between the sharp rocks and said with horror in his voice, ‘This is madness.’

‘You’re not obliged to take this way,’ said the old man. ‘I can understand your uncertainty. We’ll go back, if you like. I’ll give you a strong, experienced horse who will take you down the short cut.’

Mustela’s eyes hadn’t left the swirling current, as though he had been bewitched by it. ‘I’ll end up smashed against the rocks,’ he whispered, ‘it’s so dark down here. . or I’ll die of the cold.’

‘Half make it,’ muttered the old man.

‘And half don’t,’ Mustela replied.

The old man shrugged, as if to say, ‘So what?’, and Mustela realized with a rush how stupid he’d been to pay so much for a passage to Hades. But evidently his terror conflicted with the even greater fear of being required to explain why he had failed.

In the end, with a deep sigh, he lowered himself into the torrent, holding on to the river rocks in an attempt to steady himself. He fought against the current briefly, then slowly let himself go and was sucked into the darkness, swallowed up by the swirling waters.

In Monte Appennino, Caupona ad Silvam, a.d. VI Id. Mart., prima vigilia

The Apennine Mountains, the Woodland Inn, 10 March, first guard shift, eight p.m.

Publius Sextius galloped along the track that wound down into the valley and then ascended again towards the summit. He was following Nebula’s map along a route that left Aemilia and cut through the mountains heading south, towards Etruria.

He rode mostly under the cover of the twisted boughs, his path lit up now and then by flashes of lightning. When the road started ascending, he slowed his pace so he wouldn’t exhaust his horse, letting him walk once in a while to allow him to catch his breath. He was a generous animal and it pained the centurion to oblige him to undergo such strain, to put his life at risk in such a desperate race against time. The rain began falling and the storm broke as he came into sight of the mansio.Just in time, as the horse was about to collapse beneath him. It seemed that one of the soldiers on guard had recognized him.