Aulus put a hand on his shoulder. ‘The bowman is as trapped as us. If we go back, he can shoot us. But if he comes after us, you will put a dagger in his guts.’

‘But he can get out any time he likes.’

‘Leaving us free to escape, and tell the world there is no daemon. Someone has gone to a lot of trouble to convince the natives that these caves are haunted by some supernatural menace.’

Without further ado, Aulus set off.

This passage through the hillside sloped upwards, running away at an angle to the right. Aulus’s torch cast bizarre patterns on the sides and ceiling as he went.

Valens took another quick look around the outcrop into the big cavern. There was no sign of the archer. He must be hidden in the outer tunnel.

Wedging the torch into a crack between himself and the opening, Valens drew his dagger, then sat with his back to the rocks.

The light of Aulus’s torch had completely disappeared.

Now his breathing was under control, Valens could hear nothing but the hiss of his torch and the subdued roar of the water. No sooner was he settled than he was up again. What if the man took the initiative? Would he hear the attacker coming? Again he peered out at the ledge. Its surface was covered with a carpet of small stones from the avalanche. That would betray any stealthy approach.

Valens settled himself to wait.

The dark hole in the cavern tugged at his thoughts, like an entrance to the underworld.Valens pictured a fanged daemon, its claws clicking on the rock wall, seeking purchase, as it hauled itself gradually up the side of the chasm.

This was nonsense. He was a rational man. There was no underworld, no realm of the dead, no daemons. The Epicureans were right. Beyond this life there was nothing but eternal unconsciousness.

Anyway, his nurse had said daemons had wings.

A faint glow heralded the return of Aulus. When his ugly features reappeared, he beckoned Valens to leave his torch burning where it was lodged, and follow. They moved quietly, hoping the archer would not hear them depart. Valens could not help looking nervously back over his shoulder.

*

When they had put some distance between themselves and their attacker, they came out into another hollow chamber. The floor here was thick with mud and bat droppings. Aulus propped his torch in the filth, and pointed upwards. Despite his companion’s torch, Valens saw the tiny chink of light.

The shaft was some eight feet up. It was exceedingly narrow, surely too narrow to admit a grown man. Its sides were slippery and covered in moss. Valens’s spirit sank. Up there was fresh air and daylight, up there you could move without restriction. It was so close. They could see freedom, but it was out of reach.

‘Lift me on your shoulders,’ Aulus said.

‘You will never fit.’