'Stranger things have happened.' I spoke with care. Helena was watching me thoughtfully. 'The East is a lively arena at present. People are talking about the place all the time. Since Jerusalem was captured, the whole area is opening up for expansion.'

'So that's it!' Helena muttered. 'I knew you were up to something again.'

Thalia looked surprised. 'You're really going to Syria?'

'Somewhere close, possibly. Proposals have been whispered in my direction.' For a moment it had seemed easier to break the news to Helena with a witness who was strong enough to prevent me from being beaten up. Like most of my good ideas, I was rapidly losing faith in this one.

About a month later. The scene is set initially in Petra, a remote city in the desert. Dramatic mountains dominate on either side. Then on rapidly to Bostra.

SYNOPSIS: Falco, an adventurer, and Helena, a rash young woman, arrive in a strange city disguised as curious travellers. They are unaware that Anacrites, a jealous enemy, has transmitted news of their visit to the one man they need to avoid. When an unpleasant accident befalls Heliodorus, a theatrical hack, their help is enlisted by Chremes, an actor-producer, but by then everyone is looking nervously for a quick camel ride out of town.

We had been following the two men all the way to the High Place. From time to time we heard their voices ringing off the rocks up ahead of us. They were talking in occasional short sentences, like acquaintances who kept the politeness going. Not lost in a deep conversation, not angry, but not strangers either. Strangers would have either walked along in silence or made more of a sustained effort.

I did wonder if they might be priests, going up for a ritual.

'If they are, we should turn back,' Helena suggested. The remark was her only contribution so far that morning. Her tone was cool, sensible, and subtly implying that I was a dangerous idiot for bringing us here.

A staid response seemed called for; I put on a frivolous manner: 'I never intrude on religion, particularly when the Lord of the Mountain might demand the ultimate sacrifice.' We knew little of the Petrans' religion, beyond the facts that their chief god was symbolised by blocks of rock and that this strong, mysterious deity was said to require bloodthirsty appeasement, carried out on the mountaintops he ruled. 'My mother wouldn't like her boy to be consecrated to Dushara.'

Helena said nothing.

Helena said nothing, in fact, during most of our climb. We were having a furious argument, the kind that's intensely silent. For this reason, although we heard that the two men were toiling up ahead of us, they almost certainly failed to notice that we were following. We made no attempt to let them know. It seemed unimportant at the time.

I decided that their intermittent voices were too casual to cause alarm. Even if they were priests they were probably going routinely to sweep away yesterday's offerings (in whatever unlikeable form those offerings took). They might be locals making the trip for a picnic. Most likely they were fellow visitors, just panting up to the sky-high altar out of curiosity.

So we clambered on, more concerned about the steepness of the path and our own quarrel than anybody else.

There were various ways to reach the High Place. 'Some joker down by the temple tried to tell me this route is how they bring the virgins up for sacrifice.'

' You've nothing to worry about then!' Helena deigned to utter.

We had taken what appeared to be a gentle flight of steps a little to the left of the theatre. It rapidly steepened, cutting up beside a narrow gorge. We had the rock face on both sides at first, quarried intriguingly and threatening to overhang our way; soon we acquired a narrow but increasingly spectacular defile to our right. Greenery clung to its sides – spear-leafed oleanders and tamarisk among the red, grey and amber striations of the rocks. These were most eye-catching on the cliff face alongside us, where the Nabataeans had carved out their passage to the mountaintop taking their normal delight in revealing the silken patterns of the sandstone.

This was no place for hurrying. The twisting path angled through a rocky corridor and crossed the gorge, widening briefly into a more open space where I snatched my first breather, planning several more before we reached the uppermost heights. Helena paused too, pretending she had only stopped because I was in her way.

'Do you want to get past me?'

'I can wait.' She was gasping. I grinned at her. Then we both turned to face out across Petra, already a fine view, with the widest part of the gravelly road in the valley below snaking away past the theatre and a bunch of tasteful rock-face tombs, then on towards the distant town.

'Are you going to fight with me all day?'

'Probably,' growled Helena.

We both fell silent. Helena surveyed the dusty thongs of her sandals. She was thinking about whatever dark issues had come between us. I kept quiet too, because as usual I was not entirely certain what the quarrel was about.

Getting to Petra had been less difficult than I had feared.

Anacrites had taken great pleasure in implying that my journey here posed intolerable problems. I simply brought us by sea to Gaza. I had 'hired' – at a price that meant 'bought outright' – an ox and cart, transport I was used to handling, then looked around for the trade route. Strangers were discouraged from travelling it, but caravans up to a thousand strong converged on Nabataea each year. They arrived in Petra from several directions, their ways parting again when they left. Some toiled westwards to northern Egypt. Some took the interior road up to Bostra, before going on to Damascus or Palmyra. Many crossed straight to the Judaean coast for urgent shipment from the great port at Gaza to the hungry markets in Rome. So with dozens of merchants trekking towards Gaza, all leading immense, slowly moving strings of camels or oxen, it was no trouble for me as an ex-army scout to trace back their route. No entrepot can be kept secret. Nor can its guardians prevent penetration of their city by strangers. Petra was essentially a public place.

Even before we arrived I was making mental notes for Vespasian. The rocky approach had been striking, yet there was plenty of greenery. Nabataea was rich in freshwater springs. Reports of flocks and agriculture were correct. They lacked horses, but camels and oxen were everywhere. All along the rift valley was a flourishing mining industry, and we soon discovered that the locals produced pottery of great delicacy, floral platters and bowls in huge quantities, all decorated with panache. In short, even without the income from the merchants, there would be plenty here to attract the benevolent interest of Rome.

'Well!' Helena let slip. 'I reckon you can report back to your masters that the rich kingdom of Nabataea certainly deserves inclusion in the Empire.' She was insultingly equating me with some mad-eyed, province-collecting patriot.

'Don't annoy me, lady – '

'We have so much to offer them!' she quipped; beneath the political irony was a personal sneer at me.

Whether the rich Nabataeans would see things our way might be a different cask of nuts. Helena knew that. They had guarded their independence with skill for several centuries, making it their role to keep the routes across the desert safely open and offer a market to traders of all kinds. They were practised in negotiating peace with would-be invaders, from the successors of Alexander to Pompey and Augustus. They had an amiable monarchy. Their present king, Rabel, was a youth whose mother was acting as regent, an arrangement that seemed to be non-controversial. Much of the routine workload of government fell to the Chief Minister. This more sinister character was referred to as The Brother. I guessed what that meant. Still, so long as the people of Petra were flourishing so vibrantly, I dare say they could put up with somebody to hate and fear. Everyone likes to have a figure of authority to mutter about. You can't blame the weather for all of life's ills.