‘What’s that? What’s that?’ Caligula came striding back up the path. ‘I want to go to Rome, Macro!’

‘Very soon, Excellency.’

‘I want to see my sister, Drusilla. Have you seen Drusilla, Parmenon?’ Tears glistened in his eyes. ‘She’s beautiful. She’s got breasts.’ He pointed to a statue of Venus. ‘And her bottom; I always said she had the sweetest bottom in Rome. Have you seen her, Parmenon? I am going to make her Empress.’

I had seen Drusilla on one occasion, a lithe, olive-skinned girl. I’d also heard rumours of how Caligula’s aunt had found brother and sister in bed together.

‘You can’t have ever seen my sister,’ Caligula continued, tapping me on the shoulder. ‘If you had, you would be full of her praises.’ He slurped from the wine cup. ‘So, when is the old goat going to die, Macro? And why are you here, Parmenon?’

He turned away and talked over his shoulder. ‘Where’s Gemellus?’

‘Your Excellency,’ Macro soothed. ‘Parmenon brings messages from your sister Agrippina.’

‘Oh, the sly one, the sly one!’ Caligula’s fingers went to his mouth, deep in thought.

Darkness was falling. The breeze from the sea had turned cold. It brought a smell of olives, figs and salt. The sky was filling with cloud, dark blotches hiding the stars. The trees rustled and shook. I felt frightened. This truly was a place of demons. I wished I was back in Rome.

Caligula took a deep breath.

‘It’s good to see you, Parmenon.’ His tone had changed. He linked his arm through mine as if we were the best of friends. ‘Have you ever been to Misenum before? You should come more often: the mussels are marvellous. You are going to have supper with us, aren’t you? The old goat thinks if he keeps eating he’ll keep living.’ He sniggered beneath his breath, stopped and looked at my head. ‘You’ve got a full head of hair, Parmenon. Isn’t it a pity we can’t exchange heads?’

His face came forward as if expecting an answer. Agrippina had told me to take care over this, never to stare at Caligula’s hair or mention his increasing baldness. He tapped his forehead.

‘A wasted dome,’ he muttered. ‘Isn’t it, Parmenon?’

I looked over his shoulder. Macro’s eyes were watchful.

‘Excellency,’ I replied. ‘You have the face and head of an Emperor. You have the face and head of a God. You are not like us mere mortals.’

Caligula threw his head back in a raucous laugh. He seized my face between his hands and kissed me full on the lips. ‘When you first came to Capri, Parmenon, I knew you were touched. He has visions, Macro! I’ll never forget what you said.’

Then the lunatic was off, striding up the path, arms swinging, chuckling loudly to himself.

By the time the guards allowed us into the Emperor’s supper room, Caligula was transformed, quietly composed. Macro introduced me but all I could see was a figure sitting in the darkness.

‘Come here!’ The voice was full and strong.

I stepped into the pool of light before the couch and dropped quickly to my knees.

‘Who are you? Look at me!’

Tiberius’s face was ghastly: it was a dirty white, with the lines round his mouth more pronounced and the cheeks sunken. The sores had got worse, so that now it was a suppurating mess, from which the slanted eyes gleamed frenetically. I didn’t know whether it was due to the fever, the poison or the light from the oil lamps. Tiberius scratched one of the ulcers on his face and touched my cheek.

‘Parmenon! Have you brought news?’

‘Excellency,’ Macro replied. ‘He comes from Rome, where all is well.’

‘Now that’s a lie. Rome is never well. Sit down, sit down!’

I took my place on the couch provided. The table was laid simply, with bread, figs, some apples, cherries, stuffed dates and an amphora of wine. The meal was eaten in silence. Afterwards the Emperor’s physician Charicles came in and sat on the edge of the Emperor’s couch. The Emperor greeted him, hand extended. Charicles’s fingers rested on the Emperor’s wrist as if taking his pulse: Tiberius didn’t seem to be aware of this. Charicles looked at Macro and nodded. Caligula got up and brought across his own cup of wine, and Tiberius drank from it. Macro started some innocuous conversation but I was hardly listening. It was one of the strangest supper parties I had ever attended. Tiberius began to groan and moan, gesturing with his fingers for Macro to keep quiet, and the cup Caligula had given him fell from his hand. Charicles, assisted by Macro, helped Tiberius to his feet, and Caligula came to help. I was instructed to follow as they half carried the Emperor from the dining-room along a marble passageway to his private bedchamber. No guards challenged us, no one interfered. The bed chamber smelt stale and musty. Once the door was closed, all protocol was dropped. Tiberius was tipped on the bed, his head made comfortable on the bolsters.

‘I have done what I can.’ Charicles spoke through the darkness. ‘I can do no more.’

He left. Caligula lit an oil lamp, hands shaking.

‘It must be tonight.’ Macro stood on the far side of the Emperor’s bed. ‘Tiberius must never leave for Capri.’

The Emperor moaned and groaned, his head thrashing from side to side. Macro ordered me to bring a lamp across. He pulled back Tiberius’s eyelids and felt the pulse in his throat.

‘Weak,’ he muttered. ‘He’ll never last the night.’

Caligula was breathing heavily like an athlete who’d run far and fast, a hoarse, rasping sound which jarred the nerves and prickled the hair on the nape of my neck.

‘If he leaves for Capri,’ Macro repeated, ‘we’ll all be in danger!’ He brought a sheet up and tossed it across the Emperor’s chest. ‘We will all stand guard.’

We left the chamber and waited outside. The night wore on, until, just before dawn, Charicles returned. Macro led him into the bedroom, and I heard a shout of triumph. Charicles came out followed by a grinning Macro.

‘The Emperor is dead!’ Macro grasped Caligula’s right arm and raised it. ‘Long live the Emperor!’

It was as if the clouds had lifted and the very walls had ears. Within a short space of time the news had swept through the villa. Macro and Agrippina had organised everything well. The Praetorian Guard assembled outside the main entrance, joined by the household as well as visiting senators, as Macro led Caligula out, with me trailing behind. In the presence of all, Macro placed Tiberius’s great seal ring on Caligula’s finger. The guards drew their swords and clashed their shields, proclaiming Caligula as Emperor. His elevation to the purple was greeted by a roar of approval. I could already see small clouds of dust round the gate as horsemen left for Rome. Charicles crept up beside me, pale, sweaty and shaking.

‘What’s the matter, man?’

‘Tiberius!’ The word croaked from the back of his throat. ‘He’s alive!’

The word spread like a ripple. Macro spun round, his swarthy face pale. Caligula became like a little boy lost, shoulders hunched, he stared open-mouthed then gibbered with fright. Somehow the whisper reached the men below, and the Praetorian Guard became restless. The crowd began to break up and drift away.

‘It can’t be! It mustn’t be!’ The words slipped out of my mouth.

All I could think of was Agrippina’s face. If Tiberius lived another day, Caligula would go into the dark, his sister with him. I doubted if I’d survive long either.

I ran back into the building and down the passageway. The patter of footsteps behind told me that Macro and Caligula were following. I burst into the bedchamber. Tiberius was standing in his night shift, those hideous eyes glaring at me. He brought his hand up, fingers splayed.

‘Where is my ring?’ The voice was strong. ‘Parmenon, that’s your name, isn’t it?’ He pointed a bony finger. ‘You were sent by that bitch in Rome.’

Macro and Caligula followed me into the bedchamber. .