Caesar reached up to massage his temples with a thumb and forefinger. Through the gap in the shutters, he observed that the sky was no longer black, but dark blue: a sensible man would have headed to bed hours ago. He pushed himself out of his gilded chair and stretched, feeling the bones in his neck and back crack. There was a spot somewhere deep in his right shoulder that ached no matter what he did. He walked over to the window and heaved the shutters open wider so he could stare out into the night. The cool air was refreshing, although the stink of the harbour below had a similar, if less pleasant, enervating effect. The only sounds were the slap of waves against the harbour wall, the creak of wood afloat, and the odd shout or burst of song from one of the wharfside taverns. Across the water, the blazing flame at the summit of the Lighthouse danced in the wind, beckoning to ships far out at sea. Out of habit, he peered down into the black to check that an assassin hadn't been dispatched to climb the wall, then, as usual, silently berated himself for entertaining such a ridiculous notion. This snake pit had him wound tighter than a Vestal: it had been a long time since he had been hunted.

Titus Faberius, Caesar's veteran chief secretary, perched on a stool in the corner of the large room that had been designated the general's personal workspace and audience chamber. He had wedged a leather scroll bucket between his knees and was rummaging through it like a fox through a rubbish heap. He bellowed out a yawn, which the bucket amplified, reminding Caesar vividly of the lowing of the enormous cattle they had encountered on the banks of the Rhine a few years ago. The impulse to imitate him was becoming difficult to repress. He let his eyes close for a moment.

As usual, he immediately saw Gnaeus Pompeius' severed head, dripping natron. His broad, cheerful face, sickeningly grey and misshapen, grimacing like an actor's mask; that famous shock of hair Caesar had always envied him, hanging from an Egyptian fist, taut skin exposing the yellowed sclera of his eyes. He didn't try to blink the image away: it was a useful reminder not to let his guard down for a moment.

Young King Ptolemy's ministers had gleefully presented him with what remained of the man they called his enemy shortly after he had landed in Alexandria some weeks before. The ignorant cretins had thought their macabre gift would buy them his favour. At the time, he had masked his anger and outrage, displaying instead his genuine grief for one of Rome's greatest men, who had not so many years before been both his political ally and his son-in-law. As he had intended, this unexpected reaction dissolved their smug confidence: they offered no resistance at all to him and his officers occupying a wing of the palace nor to his men bedding down in the barracks of the royal guard.

Robbed of his reconciliation with Pompeius, Caesar had consoled himself with the thought of at least having the opportunity to reclaim the substantial debt the Ptolemies owed him for negotiating their alliance with Rome over a decade before, but within days Potheinus had returned to Alexandria along with his boy-king, armed with the knowledge that Caesar only had four thousand men with him, and any hopes he might have had for a productive – and short – visit to Egypt shrivelled and died. Potheinus would have preferred a dose of plague to giving any Roman what he asked for and point-blank refused to hand over the money. Gallic recalcitrance had been much easier to deal with: you just bombarded their turf walls and set light to their thatch until they gave you what you had asked for. Until his reinforcements arrived, that tactic just wouldn't work in Alexandria. For one thing, the Egyptians guarded their gold much more effectively than the Gauls in stone-built vaults, the location of which he had so far been unable to discover. For another, he just didn't have enough men to force the issue: if he started tearing apart the Royal Quarter looking for treasure, the Romans wouldn't just have the royal guard to deal with, but most likely half the wild population of Alexandria as well. No, the only way to reclaim what was owed him was to persuade Ptolemy to give it to him freely, and, as things stood, he judged that improbable.

Fortunately, Egypt had another Ptolemy to fall back on.

The king's older sister, Cleopatra, had been driven into exile several months before. She had been lurking in the desert with whatever ragtag army she had managed to recruit ever since. His agents had doggedly tracked her down and handed over Caesar's letter offering his support if she wished to retake her throne. Her record as queen suggested she was a realist when it came to Egypt's client relationship with Rome, and likely to be a useful counterpoint to her brother's surly councillors.

Divide and conquer: his favourite strategy.

The prefect of his personal guard knocked and was admitted to deliver his nightly report. Gaius Julius Rufio was the son of the manager of Caesar's country estate in the Alban Hills, his father liberated from slavery long before the boy was born. He was intelligent, scrupulous, and not too proud to fix a fence or dig a ditch: Caesar would readily have allowed him to replace his father when the old man retired. Rufio, however, had been set on a military career, and so, on his seventeenth birthday, he had marched hundreds of miles north to join his patron in Gaul just before his first invasion of Britannia. Caesar had kept a close eye on him, and transferred him to his praetorian cohort after three seasons of exemplary soldiering.

His men had checked the rooms thoroughly, the young man insisted. There were no nooks and crannies where an assassin might hide, nor space in the cupboards and chests. They had shaken out all the bedding hunting for snakes and scorpions, peered under the beds themselves, and checked behind the tapestries and curtains. Everything was ready, should the general wish to retire. Caesar detected the plea in Rufio's mild suggestion: the boy had purple smudges under his eyes and his shoulders slumped ever so slightly.

'Soon, Rufio, but I have a few letters to compose first.' Faberius groaned softly in his corner. Caesar ignored him. 'What are our Egyptian friends up to tonight?'

'Not a lot, sir. If anything, they're quieter than usual.'

Caesar frowned. 'That makes me uneasy, Rufio. How often are you changing the guard on my door at the moment?'

'Every four hours, general.'

'Let's reduce each shift to two. I don't want the boys getting bored just in case Potheinus is up to something.'

Rufio opened his mouth and closed it, then opened it again. He still wasn't used to his commander caring overmuch about his personal safety. 'Do you think that's likely, sir?'

'Probably no more than usual, Rufio, but the longer we occupy the palace, the harder that gods-cursed eunuch is going to try to find a way to kill me. Wouldn't you do the same if you owed a man forty million sesterces and had no intention of paying him?'

'I certainly bloody would,' muttered Faberius, who had abandoned his bucket and was gathering up wax tablets.

'Just say the word, general, and I'll saw a hole in the eunuch's gut myself.'

Caesar smiled tightly. This boy would have been wasted growing grapes. 'I appreciate the thought, Rufio. The time may come for more direct action, but I have a few more moves to make first. Now, go on and get yourself to bed.'

When the prefect had left, Faberius yawned again. He had seated himself behind his small writing table with an iron stylus poised above a blank tablet, resigned to at least another hour's work. 'Ready when you are, Caesar.'

'No, Titus, you can go too. I haven't forgotten how a pen works.'

'Can't whatever it is wait until morning? When was the last time you slept more than a few hours together?'

Caesar grimaced: he disliked this tendency in Faberius to fuss and it irritated him that he couldn't immediately think of the answer. 'I honestly can't remember, Titus. Certainly not since we arrived in Alexandria. The night after Pharsalus, perhaps?'

'I definitely didn't go to bed that night,' said Faberius, grinning. 'Pompeius left us too much vintage wine to drink. I woke up the next morning propped up against a tent pole with one of those huge hounds they have up there pissing in my lap. Gods, the smell! Almost enough to snap me out of my hangover instantly.'

'I seem to remember I got no work out of you that day.'

'First day off I'd had in a decade.'

Caesar was about to reply when a small sound in the corner of the room pulled his head around like a loosed catapult. The grinding of stone on stone. Faberius heard it too. 'Shit,' he pronounced. He only had his sharp stylus to protect himself; Caesar's fingers found the ivory and leather grip of his sword, which he always kept belted at his waist even when he wasn't armoured.

'I'll be having words with Rufio,' he said grimly. 'Guards!'

The grand cedarwood doors were so thick that he had to shout once more at full battlefield volume before they slammed open and Calidius and Cornelius of the Sixth hurtled in, eyes darting about looking for the threat.

Caesar waved them to a halt. All five men – Meles, his sharp-eared servant, had skidded in as well – stared at the figure who had emerged from the wall beside a wall-hanging depicting the energetic coupling of Zeus and Leda.

So there was a secret door after all. Rufio had checked repeatedly for one, the Ptolemies' habit of poisoning and hacking each other to death being notorious, but failed to find any hollow spaces or tell-tale draughts. The door must be so well-constructed that the edges were completely indistinguishable from the natural gaps between the stone. Murderers and traitors these Ptolemies might be, but they were damned fine engineers.

The fellow moved slowly, his hands raised in the universal gesture of submission. He lowered his hood and pulled back his cloak to show he wasn't armed. His shoulders could easily bear a bull calf, though, and his broken nose suggested experience in the boxing or wrestling ring: not a man to be underestimated. His tunic was plain, but of good quality, as were his high boots. When he spoke, his accent wasn't Alexandrian, but, Caesar thought, southern Italian or possibly Sicilian.

'Good evening, Dictator.' He inclined his head, in no doubt as to Caesar's identity. Caesar took his hand from his sword and returned the gesture: he was no eastern despot. 'I am Apollodorus, a friend of Queen Cleopatra.'

Caesar kept his expression mildly interested, but inside he rejoiced. He hadn't expected the queen's arrival for some time yet. Finally, he might be able to make progress. 'I assume you mean "friend" in the official court sense, Apollodorus? You are a close advisor to the queen?'

'It is my honour to offer the queen my opinion when asked, Dictator.'

'You bring a message?'

The big man smiled. 'In a manner of speaking.'

Faberius rose to stand at his patron's elbow, scenting danger. 'Caesar—'

He squeezed his friend's shoulder. 'Come on, Titus, haven't you figured it out? Please continue, Apollodorus.'

'As you wish. May I present Cleopatra VII Philopator, rightful queen of Upper and Lower Egypt, divine incarnation of Isis.'

A shadow detached itself from the darkness beyond the secret door. Caesar watched, transfixed, as it stepped towards him. He had expected her to send word when she was encamped outside the city, not run the gauntlet of her brother's guards – and his own – to meet him in secret like this. He found himself intrigued. She was swathed in a heavy himation dyed the darkest possible purple, her face veiled like a modest Athenian virgin. He remembered how young she was – just over twenty.

When she was no more than an arm's length from him, she paused. Slender fingers peeled back her mantle. She was not the most beautiful woman he had ever encountered, but her features held his attention, nonetheless. She had the prominent nose and chin of her family – how could she not when they had intermarried for generations? The broad white ribbon of Alexander's successors, pinned firmly into place for her adventure, crowned her date-coloured hair, which was divided into rolls and gathered at the back in a low bun. Plump pearls set in gold glittered below her ears.

Delicate eyebrows slightly raised, she met his gaze. Her brown eyes were her finest feature, their size accentuated by solid lines of kohl. Of a sudden, as if she had come to a decision, her expression softened.

'I feared we might find you already asleep.' Her voice was deep, every syllable a note beautifully played.

He inclined his head. 'Your timing is impeccable, Queen Cleopatra. I am Gaius Julius Caesar.'

'Thank Isis for that,' she said with feeling, making him smile. She looked around. 'I would prefer to speak alone, Caesar.'

Faberius twitched. It was a bold request, certainly, but Caesar could see no danger in it. If she were to produce a dagger from that voluminous mantle and somehow jab it between his ribs, she would kill her hopes of reclaiming her throne along with him. What intrigued him was how willing she was to risk being alone with him, a man she only knew through her father's anecdotes, the reports of her friends abroad, and a couple of brief letters.

He nodded. 'As you wish. We have a great deal to discuss.' He turned to Faberius, who was looking at him as if he needed to be tied down for his own safety. 'Titus, go and find Rufio and introduce him to Apollodorus here. Between them, they can make arrangements for the queen's people to make their way into the palace safely.'

'Shall I come back to make notes for you?'

Caesar looked back at Cleopatra, who was murmuring instructions to Apollodorus. Her himation had slipped down at the back, exposing the curve of her neck. 'I think I'll manage, Titus. After you find Rufio, get some rest: I imagine tomorrow will be an interesting day.' He levelled a stern look at the two legionaries, who were trying to look like they weren't staring at the queen. 'Back to your post, gentlemen, and make sure we're not disturbed unless the palace is on fire. Clear?'

They straighten. Caldidius is trying not to smirk, which Caesar notes for future reference when considering promotions. 'Yes, general.'

His face still roaring concern, Faberius ushered the two young men towards the door and, clearly as an afterthought, beckoned to Apollodorus, who waited for a nod from his queen and then strode after them. Out of the corner of his eye, Caesar noted Meles retreating silently to his tiny chamber. He had no doubt that his servant's ear would be pressed to the door so hard that he'd be at risk of splinters, but this didn't concern him. Meles was more an extension of himself than a person.

Within a few heartbeats, Caesar and Cleopatra were alone together.