'Not at all. You'd better tell me your reasoning.'

Grumio then went through his argument like a magician consenting to explain some sleight of hand. His voice was level and considered. As he spoke, I could almost hear myself giving this as evidence before a criminal judge. 'Everyone in the company had an alibi for the time Heliodorus was killed. So maybe, unknown to anyone, he had an outside contact at Petra. Maybe he had an appointment with somebody local that day. You say you found Musa in the close vicinity; Musa must have been the man you had followed from the High Place. As for the rest – it all follows.'

'Tell me!' I croaked in amazement.

'Simple. Musa then killed Ione because she must have known that Heliodorus had some private connection in Petra. She had slept with him; he could have said. Again, the rest of us all have alibis, but wasn't Musa in Gerasa on his own that night for hours?' Chilled, I remembered that indeed I had left him at the Temple of Dionysus while I went off to make enquiries about Thalia's organist. I didn't believe he had been to the Maiuma pools in my absence – but nor could I prove that he had not.

With Musa no longer here, I could never ask him about it either.

'And how do you explain Bostra, Grumio? Musa being nearly drowned himself?'

'Simple. When you brought him into the company, some of us thought him a suspicious character. To deflect our suspicion, he took a chance at Bostra, jumped into the reservoir deliberately, then made up a wild claim that someone shoved him in.'

'Not the only wild claim hereabouts!'

I said it, even though I had the inevitable feeling that all this could be true. When someone throws such an unlikely story at you with such passionate conviction, they can overturn your common sense. I felt like a fool, a bungling amateur who had failed to consider something right under my nose, something that ought to have been routine.

'This is an amazing thought, Grumio. According to you, I've spent all this time and effort looking for the killer when the plain fact is I brought him with me all along?'

'You're the expert, Falco.'

'Apparently not: What's your explanation for the scam?'

'Who knows? My guess is Heliodorus was some sort of political agent. He must have upset the Nabataeans. Musa is their hit man for unwelcome spies – '

Once again I laughed, this time rather bitterly. It sounded weirdly plausible.

Normally I can resist a clever distraction. Since there certainly was one political agent amongst us, and he was indeed now acting as a playwright, Grumio's solemn tale had a lurid appeal. I really could envisage a scenario in which Anacrites had sent more than one disguised menial into Petra – both me and Heliodorus – and The Brother had schemed to deal with each of us in turn, using Musa. Helena had told me Musa was marked for higher things. Maybe all the time I had been patronising his youth and innocence, he was a really competent executioner. Maybe all those messages to his 'sister' deposited at Nabataean temples were coded reports to his master. And maybe the 'letter from Shullay' he kept hoping to receive would not have contained a description of the murderer, but instructions for disposing of me:

Or rather, maybe I should lie down quietly, with sliced cucumber cooling my forehead, until I got over this lunacy.

Grumio rose to his feet with a demure smile. 'I seem to have given you a lot to think about! Pass on my regards to Helena.' I managed a wry nod of the head, and let him go.

The conversation had been devoid of clowning. Yet I was still left with the sinking sensation that somehow the joke was on me.

Very neat.

Almost, as the grim jokester Grumio himself would have said, too obvious to be true.

Chapter LX

I was dismal now. It felt like a nightmare. Everything appeared close to reality, yet was hugely distorted.

I went in to see Helena. She was awake, but flushed and feverish. I could tell by looking at her that unless I could do something, we were in serious trouble. I knew she could see I had problems I wanted to talk about, but she made no attempt to ask. That in itself was a depressing sign.

In this mood, I was hardly expecting what happened next.

We heard a commotion. The Palmyrenes were all exclaiming and shouting. It did not sound as though raiders had set upon us, but my worst fears leapt. I rushed out of the tent. Everyone else was running, all in the same direction. I felt for my knife, then left it down my boot so I could run faster.

At the roadside an excited group had clustered around a particular camel, a new arrival whose dust was still creating a haze above the road. I could see the beast was white, or what they call white in a camel. The trappings looked brighter than usual and more lavishly fringed. When the crowd suddenly spilled outwards so I had a clearer view, even to my untutored eye this was a fine creature. A racing camel, plainly. The owner must be a local chief, some rich nomad who had made several fortunes from myrrh.

I was losing interest and about to turn back when somebody yelled my name. Men in the crowd gesticulated to some unseen person who was kneeling at the camel's feet. Hoping this might be Musa returning, I walked up closer. People fell back to let me through, jostling close behind again as they tried to see what was happening. With bruised heels and a bad temper I forced my way to the front.

On the ground beside the splendid camel, a figure wrapped in desert robes was searching in a small roll of baggage. Whoever it was stood up and turned to me. It was definitely not Musa.

The elaborate head-dress was pushed back from a startling face. Vivid antimony eye paint flashed while earrings as big as the palm of my hand rattled out a joyous carillon. All the Palmyrenes gasped, awestruck. They dropped back hastily.

It was a woman, for one thing. Women do not normally ride the desert roads alone. This one would go anywhere she wanted. She was noticeably taller than any of them, and spectacularly built. I knew she must have chosen her own camel, with expertise and taste. Then she had cheerfully raced across Syria unaccompanied. If anyone had attacked her, she would have dealt with them; besides, her bodyguard was wriggling energetically in a large bag she wore slung across a bosom that meant business.

When she saw me, she let out a roar of derision, before brandishing a little iron pot. 'Falco, you miserable dumbhead! I want to see that sick girl of yours – but first come here and say a nice hello!'

'Hello Jason,' I responded obediently, as Thalia's python finally forced his head out of his travelling bag and looked around for somebody meek whom he could terrorise.

Chapter LXI

There were a lot of frightened men at this gathering, and not all of them were worried about the python.

Thalia shoved Jason unceremoniously back into his bag, then hung it around her camel's neck. With one bejewelled finger she stabbed towards the bag. Slowly and clearly (and unnecessarily), she addressed the assembled nomads: 'Any man who puts a hand on the camel gets seen off by the snake!'

This hardly squared with what she had always assured me about Jason's lovable nature. Useful, however. I could see the Palmyrenes all inclined to my own nervous view of him.

'That's a gorgeous camel,' I said admiringly. 'With a gorgeous rider whom I never expected to meet in the middle of the desert.' It seemed right, however. Somehow I felt more cheerful already. 'How in the name of the gods do you come to be here, Thalia?'

'Looking for you, darling!' she promised feelingly. For once I felt able to take it.

'How did you find me?'