Now he was near the bed, a mere hand’s breadth away from his father’s sleeping body. He reached out as gently as possible, and put his thumb and forefinger on the lid.

Immediately he felt a freezing, tight sensation, as if something were coiling round his neck.

He had to ignore it. Now was the time. As delicately as he might have held Brutus when he was a baby, he raised it from Aeneas’s neck. His father shifted, and the chain snagged on his ear. A surge of terror ran through Silvius, and he stood as still as a frightened rabbit; then, after scratching his nose and moaning something, Aeneas settled.

As steadily as he could, Silvius lifted the chain and put it carefully around his own neck, then placed the decoy around Aeneas’s neck. He had to move his father’s head a little way to do so, and pulled back quickly. Aeneas, deep in sleep, must have realised something was happening. He mumbled, and put his hand to his chest, as if seeking the casket; his fingers closed around the replacement, and he was at rest once more.

Silvius, mouth dry, tiptoed to the door, then came out, picked up his pack and made his way as quickly as possible to the eastern side of the House of the Wolf where the main latrines were. He paused for a second when he smelt the familiar tang of waste, and half-elated, half-terrified, held the casket. It was heavy in his hands, and he let it drop back against his chest, cool and dangerous.

A shadow detached itself from the greater darkness as he arrived. He said, ‘Be well, friend. The stars are bright tonight.’

‘And the moon looks down upon us kindly.’

Silvius relaxed. That was the phrase he’d agreed on with Elissa. ‘Quickly,’ he urged, as Elissa’s features became more distinct. He showed her the golden chain. She nodded, and made a small bow.

‘You did it,’ she said softly, touching his hand for a moment. ‘It’s the right thing. Apollo told me. Now let’s go.’ She shifted the small bag she’d brought around her neck.

First, Silvius climbed up the fence, using the corner of the latrine to steady himself. Without thinking too much about it, when he reached the top he turned around and let himself drop the ten feet or so, falling into a crouch. Ignoring the stink, he stood up and held out his arms for Elissa. But she dropped down beside him.

They kept to the city wall, out of the sight line of any guard who might be looking out across the plain for attackers. Soon they smelled horseflesh and manure, and knew they had reached the stables.