People kept coming up, as if to check on us. They were kind, but it meant I could never sit and think. The conversation that stays in my mind most clearly was another involving Grumio. It was the day after the accident, in fact. He turned up again, this time in a most apologetic mood.

'I feel I let you down, Falco. Over Musa, I mean. I should have told you earlier.'

'I could do with him,' I agreed tersely.

'I saw him ride off, but hardly thought he could be leaving you permanently.'

'He was free to come or go.'

'Seems a bit odd.'

'People are.' I may have sounded grim. I was feeling drawn. After a hard day on the desert road, with no hope of reaching the oasis yet at the dire pace we were travelling, I was at a low ebb.

'Sorry, Falco. I guess you're not feeling talkative. I brought you a flagon, in case it helps.'

It was welcome. I felt obliged to invite him to stay and share the first measure with me.

We talked of this and that, of nothing in particular, and of Helena's progress or lack of it. The wine did help. It was a fairly ordinary local red. Petronius Longus, the Aventine's wine expert, would have likened it to some off-putting substance, but that was just him. This was perfectly palatable to a tired, dispirited man like me.

Recovering, I considered the flagon. It was a handy size, about right for a packed lunch if you were not intending to do any work afterwards. It had a round base covered in wickerwork, and a thin, loosely plaited carrying string.

'I saw one like this at a scene I'll not forget.'

'Where was that?' asked Grumio, disingenuously.

'Petra. Where Heliodorus was drowned.'

Naturally the clown expected me to be watching him, so instead I stared into the fire as if gloomily remembering the scene. I was alert for any twitches or sudden tensions in him, but noticed none. 'These are about the most common kind you can get,' he observed.

It was true. I nodded easily. 'Oh yes. I'm not suggesting it came from the same vintner, in the same basket of shopping.' All the same, it could have done. 'There's something I've been meaning to ask you, Grumio. People have been wishing on me the idea that Heliodorus was killed because of his gambling habits.'

'You asked Tranio about it.' I was interested to hear they had conferred.

'So I did. He lost his temper,' I mentioned, now turning a calm stare on him.

Grumio cradled his chin, looking reflective. 'I wonder why that could be?' He spoke with the light twist of malice I had heard from him before. It was hardly evident – could have been an unfortunate mannerism – except that one of the times I had heard it was when he was entertaining the crowd at Gerasa by hurling a knife at me. I remembered that rather clearly.

I stayed calm. 'The obvious reason is he had something to hide.'

'Seems a bit too obvious, though?' He made it sound like a question I should have thought of for myself.

'There has to be some explanation.'

'Maybe he was afraid you had found out something that looked bad for him.'

'That's a good thought!' I replied brightly, as if I had been incapable of it myself. We were sparring here, each pretending to be simple. Then I let a growl slink back into my voice. 'So tell me about you and your tentmate playing dice with the playwright, Grumio!'

He knew there was no point denying it. 'Gambling's not a crime, is it?'

'Nor is having a gambling debt.'

'What debt? Playing was just a lark from time to time. We soon learned not to bet seriously.'

'He was good?'

'Oh yes.' There was no hint that Heliodorus might have cheated. Sometimes I wonder how gambling sharks get away with it – and then I talk to an innocent minnow, and realise.

Tranio might know that Heliodorus had weighted his dice; I had wondered about that when I talked to him. So now I considered the interesting prospect of Tranio perhaps keeping this information from his so-called friend. Just what was the relationship between these two? Allies covering up for each other? Or a pair of jealous rivals?

'So what's the big secret? I know there must be one,' I urged him, putting on my frank, successful-informer air. 'What's Tranio's beef?'

'Nothing big, and not a secret.' Not now, anyway; his friendly tentmate was about to land him in it without compunction. 'What he was probably loath to tell you was that once, when he and I had been having an argument, he played with Heliodorus while I was off on my own – '

'With a girl?' I too could be disingenuous.

'Where else?' After my chat with Plancina, I didn't believe it. 'Anyway, they were in our tent. Tranio needed a forfeit and placed something that wasn't his, but mine.'

'Valuable?'

'Not at all. But as I felt like having a wrangle I told him he had to get it back from the scribe. Then, you know Heliodorus – '

'Actually, no.'

'Oh well, his reaction was typical. The minute he thought he had something important he decided to keep it and taunt Tranio. It rather suited me to keep our clever friend on tenterhooks. So I let on that I was mad about it. Tranio went spare trying to put things right, while I hid a smile and got my own back watching him.' One thing for Grumio; he possessed the full quota of the comedian's natural streak of cruelty. By contrast, I really could imagine Tranio taking the blame and becoming distraught.

'Maybe you should let him off now, if he's sensitive! What was the pledge, Grumio?'

'Nothing important.'

'Heliodorus must have believed it was.' So must Tranio.

'Heliodorus was so dedicated to torturing people, he lost touch with reality. It was a ring,' Grumio told me, saying it with a slight shrug. 'Just a ring.'

His apparent indifference convinced me he was lying. Why should he do that? Perhaps because he didn't want me to know what the pledge really was:

'Precious stone?'

'Oh no! Come on, Falco. I had it off my grandfather! It was only a trinket. The stone was dark blue. I used to pretend it was lapis, but I doubt if it was even sodalite.'

'Was it found after the playwright died?'

'No. The bastard had probably sold it.'

'Have you checked with Chremes and Phrygia?' I insisted helpfully. 'They went through the playwright's stuff, you know. In fact we discussed it and I'm sure I remember them owning up quite freely that they had found a ring.'

'Not mine.' I thought I detected just a faint trace of irritation in young Grumio now. 'Must have been one of his own.

'Or Congrio might have it – '

'He hasn't.' Yet according to Congrio, the clowns had never asked him properly about what they were looking for.

'Tell me, why was Tranio afraid to tell me about this missing pledge?' I asked gently.

'Isn't that obvious?' A lot of things were obvious, according to Grumio. He looked remarkably pleased with himself as he landed Tranio in it. 'He's never been in trouble, certainly not connected with a murder. He overreacts. The poor idiot thinks everyone knows he had a row with Heliodorus, and that it looks bad for him.'

'It looks far worse that he hid the fact.' I saw Grumio's eyebrows shoot up in a surprised expression, as if that thought had not struck him. Somehow I reckoned it must have done. Drily, I added, 'Nice of you to tell me!'

'Why not?' Grumio smiled. 'Tranio didn't kill Heliodorus.'

'You say that as if you know who did.'

'I can make a good guess now!' He managed to sound as if he were chiding me with negligence for not guessing myself.

'And who would that be?'

That was when he hit me out of the blue: 'Now that he's skipped so suddenly,' suggested Grumio, 'I should think that the best bet is your so-called interpreter!'

I was laughing. 'I really don't believe I heard that! Musa?'

'Oh, he really took you in, did he?' The clown's voice was cold. If young Musa had still been here, even innocent, I reckon he would have panicked.