'Or bought the drink and devised the plan,' Helena agreed, as if she herself regularly did such things. 'What sort of motive do you think we are looking for?'

'I don't believe it can be money. No one here has enough of it. That leaves us with the old excuses – envy or sexual jealousy.'

'So we have to ask people what they thought of the playwright? Marcus, won't they wonder why we keep enquiring?'

'You're a woman; you can be plain nosy. I shall tell them the killer must be one of our party and I'm worried about protecting you.'

'Load of mule-dung!' scoffed my elegant lady with one of the pungent phrases she had picked up from me.

I had already seen what the theatre troupe was like. We were dealing with a fickle, feckless crowd here. We would never pin down any of them unless we set about it logically.

It had taken most of the trip just to work out who everyone was. Now we sat on a rug outside our tent. Musa was with us, though as usual he squatted slightly apart, not saying a word but calmly listening. There was no reason to hide our discussion from him so we talked in Greek.

'Right, let's survey the tattered cast list. They all look like stock characters, but I'm betting that not one of them is what they seem:'

The list had to be headed by Chremes. Encouraging us to investigate might exonerate him as a suspect – or it might mean he was cunning. I ran through what we knew about him: 'Chremes runs the company. He recruits members, chooses the repertoire, negotiates fees, keeps the cash box under his bed when there's anything in it worth guarding. His sole interest is in seeing that things run smoothly. It would take a really serious grievance to make him jeopardise the company's future. He realised that a corpse in Petra could land them all in jail, and his priority was to get them away. But we know he despised Heliodorus. Do we know why?'

'Heliodorus was no good,' Helena answered, impatiently.

'So why didn't Chremes simply pay him off?'

'Playwrights are difficult to find.' She kept her head down while she said it. I growled. I was not enjoying reading through the dead man's box of New Comedy. New Comedy had turned out to be as dire as Chremes had predicted. I was already tired of separated twins, wastrels jumping into blanket chests, silly old men falling out with their selfish heirs, and roguish slaves making pitiful jokes.

I changed the subject. 'Chremes hates his wife and she hates him. Do we know why? Maybe she had a lover -Heliodorus, say – so Chremes put his rival out of the way.'

'You would think that,' Helena sneered. 'I've talked to her. She yearns to star in serious Greek tragedy. She feels dragged down by having to play prostitutes and long-lost heiresses for this ragged troupe.'

'Why? They get to wear the best dresses, and even the prostitutes are always reformed in the last scene.' I was showing off my research.

'I gather she gives her all powerfully while longing for better things – a woman's lot in most situations!' Helena told me drily. 'People tell me her speech when she gives up brothelkeeping and becomes a temple priestess is thrilling.'

'I can't wait to hear it!' In fact I'd be shooting out of the theatre to buy a cinnamon cake at a stall outside. 'She's called Phrygia, isn't she?' The players had all taken names from drama. This was understandable. Acting was such a despised profession any performer would assume a pseudonym. I was trying to think up one myself.

Phrygia was the company's somewhat elderly female lead. She was tall, gaunt, and flamboyantly bitter about life. She looked over fifty but we were assured by everybody that when she stepped on stage she could easily persuade an audience she was a beautiful girl of sixteen. They made much of the fact that Phrygia could really act – which made me nervous about the talents of the rest.

'Why does Chremes hate her?' I wondered. 'If she's good on stage she ought to be an asset to his company.'

Helena looked dour. 'He's a man, and she is good. Naturally he resents it. Anyway, I gather he's always lusting after more glamorous bits.'

'Well that would have explained it if he had been found in the pool, and we had heard Phrygia luring him uphill.' It seemed irrelevant to Heliodorus. But something about Chremes had always bothered me. I thought about him more. 'Chremes himself plays the parts of tiresome old fellows – '

'Pimps, fathers and ghosts,' Helena confirmed. It didn't help.

I gave up and tried considering the other actors. 'The juvenile lead is called Philocrates. Though he's not so juvenile if you look closely; in fact he creaks a bit. He takes on prisoners of war, lads about town, and one of the main set of twins in every farce which has that gruesome identity mix-up joke.'

Helena's summary was swift: 'A dilettante handsome jerk!'

'He isn't my chosen dinner companion either,' I admitted. We had exchanged words on one occasion when Philocrates had watched me trying to corner my ox to harness it. The words were cool in the circumstances – which were that I asked his assistance, and he snootily declined. I had gathered it was nothing personal; Philocrates thought himself above chores that might earn him a kicked shin or a dirty cloak. He was high on our list to investigate further when we could brace up to an hour of insufferable arrogance. 'I don't know who he hates, but he's in love with himself. I'll have to find out how he got on with Heliodorus. Then there's Davos.'

'The opposite type,' Helena said. 'A gruff, tough professional. I tried to chat with him, but he's taciturn, suspicious of strangers, and I guess he rebuffs women. He plays the second male lead – boasting soldiers and such. I reckon he's good -he can swagger stylishly. And if Heliodorus was a liability as a writer, Davos wouldn't think much of it.'

'I'll watch my step then! But would he kill the man? Davos might have despised his work, but who gets shoved in a pool for bad writing?' Helena laughed at me suggestively.

'I rather took to Davos,' she grumbled, annoyed with herself for being illogical. Somehow I agreed with her and wanted Davos to be innocent. From what I knew of Fate, that probably put poor Davos at the top of the suspects list.

'Next we have the clowns, Tranio and Grumio.'

'Marcus, I find it hard to tell the difference between those two.'

'You're not meant to. In plays that have a pair of young masters who are twins, these two play their cheeky servants -also identical.'

We both fell silent. It was dangerous to view them as a pair. They were not twins; they were not even brothers. Yet of all the company they seemed most inclined to carry over their stage roles into normal life. We had seen them larking about on camels together, both playing tricks on the others. (Easy to do on a camel, for a camel will cause trouble for you without being asked.)

They went around in tandem. They were the same slim build – underweight and light-footed. Not quite the same height. The slightly taller one, Tranio, seemed to play the flashy character, the know-all city wit; his apparent crony, Grumio, had to make do with being the country clown, the butt of sophisticated jokes from the rest of the cast. Even without knowing them closely I could see that Grumio might grow tired of this. If so, however, surely he was more likely to put the boot into Tranio than strangle or drown the playwright?

'Is the clever one bright enough to get away with murder? Is he even as bright as he likes to think, in fact? And can the dopey one possibly be as dumb as he appears?'

Helena ignored my rhetoric. I put it down to the fact that only senators' sons have rhetoric tutors; daughters need only know how to twist around their fingers the senators they will marry and the bathhouse masseurs who will probably father those senators' sons.