"I know Antheses is locked up and you've given him a good long sentence for duping the widow out of her husband's money - how Faustinius came by it we'll never know, now she's gone. But I have this horrible feeling that he'll manage to give us the slip and get out."

"Well, if he does, he'll go in the opposite direction as us, so he'll be someone else's problem."

"I wanted to tell you as soon as the arm was discovered to keep an eye on him, but I only had gossip and rumour that he was seen coming and going from Faustinius's villa. They were working together on some scheme. But I only thought he might lead us to the killer."

"Every time we questioned him we got a different story. You can forget him now - you've done a good job, Brutus."

"I never suspected he might've killed Faustinius, because I thought he needed the merchant more than the merchant needed him. People like Antheses are ten a penny. Faustinius, he was the clever one."

"And the lucky one, married to Sahia, most would agree. Wherever she is, we wish her well. She knows her children are safe with my wife, and they're good companions for our children. Now Brutus, forget Isca - keep your eyes on the road ahead."

Lucan stretched, luxuriating in the press of Sahia's naked body next to his. When she came to him begging for his help, he knew instantly what to do. A friend of his had left this small dwelling an hour's ride from Isca, and he had helped her flee. As soon as the Legion marched away, he had come to her and they had embraced and - he dropped a kiss on her forehead. For him it was passion, for her - perhaps comfort, at the moment, but who knew where it might lead?

And finally she had revealed to him why she had been so afraid. That foolish husband of hers had double-crossed the Silurians he traded with. He'd given them short measure, increased his prices - he'd been overconfident. No wonder they'd set their Druids on him. And Sahia was terrified they'd come for her too.

Silly girl, he thought, stroking her rounded hip. At least he wouldn't have to double-cross anyone to shower her with gold and presents. His family had money enough to keep Sahia happy. One day they might even send for her children, safe with Modestina Publius, when things had quietened down.

Mind busy with happy plans, Lucan too fell asleep.

Antheses watched the dust settle after the last soldiers marched out of the fort, and felt a great stillness fall. All the hustle and bustle was gone. This was going to be a dull place, he thought. Where should he head for next? Hibernia possibly, or maybe Gaul - yes, Gaul was probably a land of opportunity for men such as himself.

He sat on the hard stone floor and took out his dice and began to play with them. Funny how thoughts kept coming back to you when it was still and quiet. Thoughts you didn't want. Like the look on Faustinius's face when he'd cut his throat. He looked so surprised. Like he didn't believe it was happening. The blood - the blood kept coming . . .

Antheses tossed the dice, scooped them up, tossed again. That's when he'd had the idea - he'd heard all about those wild men and their barbarian ways. Human sacrifices - ugh. At least that had worked. Everyone had fallen for it, even the Silurians. They were just glad Faustinius was dead. If he hadn't got him, they would have, in revenge for his double-dealing.

No, Faustinius had only himself to blame. He'd been just too clever for his own good. Coming back upriver like that, bursting with pride at all his clever deals, boasting to Antheses. Then letting slip about the hoarded gold. The picture of it had burst in Antheses' mind like a rising sun. Such a golden opportunity - to end the life he'd led till then, somehow he would become a man of substance, invent a new Antheses who wouldn't be looked down on, have to do the worst jobs to eke a living. The knife had been in his hand before he even knew it and then - Then he just had to dispose of the body. The coracle would lead everyone to the Silurians. But the arm in the hypocaust - well, that had been his bit of fun. He couldn't resist it. So close to the truth, and no one even guessed. But the cutting, that had been hard - No, he would get rid of these thoughts. He tossed the dice again, then called out, "Antoninus, fancy a game? Now, what shall we use for stakes?"

Caveat Emptor by Rosemary Rowe When I compiled Classical Whodunnits in 1996 I was delighted to publish the first story featuring Libertus the Pavement-Maker, and he has since gone on to feature in a series of popular novels starting with The Germanicus Mosaic (1999). Libertus is a freedman and craftsman who lives in the city of Glevum (what is now Gloucester) in Britain at the end of the second century. This story takes place seventy years from the previous, to a time when Roman Britain was at its most prosperous.

To most of us an iron knife is just an iron knife. Of course, there are different qualities of blade, which is why some of them become almost magical, though I bought one from a pedlar once which would scarcely cut a piece of cheese. Mostly, however, knives are simply things for carrying in one's belt, useful if one is unexpectedly invited out to dine, or as a scant protection against bandits, wolves or bears while travelling. Scarcely a commodity to risk execution for. Yet there is the curious case of Calvus, who did exactly that.

His real name isn't Calvus, obviously. Few people are called "Baldy" legally, but since he hailed from Gaul and had a name which no one could pronounce, Calvus he instantly became. And it was as Calvus the meat-butcher that he sent word to me, when he was captured and locked up in the Glevum market cells.

I knew him only slightly, and liked him even less. He was a small, fat swarthy man, bald as a pig, with a smile as unpleasant as any of his wares. Standing at his marcellum, his market stall, with a hatchet in his hand, spattered from head to foot with blood and entrails, and surrounded by bleeding carcasses, he was a fearsome sight. Mothers murmured, "Calvus will get you" when children disobeyed.

It was Junio, my slave, who brought me the news. I'd sent him to collect water from the town fountain, and when he returned, he came panting into my rickety workshop to say, "Master, Calvus the butcher is in jail, and I am sent to ask if you will speak to him."

I put down my selected tiles with a grunt. I was engaged on a complex piece of work, a decorative panel in honour of the impending visit of an ambassador from Rome. I was assembling it on a piece of hessian and was hoping to take it to the council chambers on my handcart the next afternoon. With a little planning, I could take out a section of the existing tiles and put my insert in, while all the councillors were busy at the baths. It is a technique I have perfected over years, and it requires concentration on my part. I was not pleased to be interrupted by a summons from a common butcher who had no rank at all.

I bridled. "He sends a message, does he? I wonder how many guards he had to bribe for that." Common prisoners in the filthy Glevum jail are not usually privileged to summon friends.

Junio gave his cheekiest grin. "You forget, master, he is one of Marcus's clientes. No doubt that's why he asked for you."

It was true, I had forgotten that. Calvus had first come to Glevum as a gift, to Marcus Aurelius Septimus (one of the most powerful men in the entire province of Britannia) from a friend. He was then a kitchen-slave, but Marcus had permitted him to buy his freedom shortly afterwards partly, I suspect, because he didn't like Calvus any more than I did. So Calvus was legally Marcus's freeman - which meant that he had lifelong duties to his patron, naturally, but also that Marcus was more or less obliged to offer protection in return. Which, unfortunately, was where I came in. Marcus Aurelius Septimus is my patron too.

"Marcus suggested it?" I said, knowing what the answer was. I've solved a few crimes for Marcus in the past, and he has formed a habit of involving me. I got up resignedly and gestured for my cloak. No question, now, of my refusing this or I was likely to end up in the cells.

I didn't take Junio with me to the jail. I'd spent a day and night there once myself. The cells are filthy, stinking, dark and damp and men are shackled to the floor like animals: not a place to take an impressionable boy My decision wasn't very wise perhaps, since, seeing me turn up at the gates tunic-clad and without an attendant slave, the guard on duty almost refused to let me in.

I almost pointed out that I was a full Roman citizen, but remembered that, in that case, I was supposed to wear a toga on business at all times. I let the matter rest. I said, humbly, "His Excellency Marcus Aurelius Septimus required me to come. One of his clientes is in jail."

The soldier looked me up and down. "Calvus the butcher, is it? I was warned to expect somebody for him. Through that door there, in the jailer's house."

I should have predicted that. Having a powerful patron won you certain rights. It wasn't like being a citizen, of course (Calvus wasn't born in Glevum, which would have given him automatic rights) but Marcus's name was sufficient to ensure that our interview would not take place in the foul darkness of a cell. Indeed, the room I was shown into was a pleasant one, with a shuttered window space and a rough stool and table set for me. There was even a jug of cheap watered wine, and a few battered-looking dates.

Calvus looked in worse condition than the fruit. His legs were bruised, his clothes were torn, and a bloodied blackness round his eyes and mouth suggested a less-than-gentle arrest. Before they found out who his patron was, the jailers had obviously chained him up "slave-wise", with a collar around the neck linked to his arms and feet. The victim cannot stand upright, nor move without half-strangling himself. Of course, these bonds had been removed by now, but Calvus still walked painfully.

The big guard who had brought him in prodded him towards me with his sword and winked. "All yours," he said. "And welcome to him, too. I was told that you could talk to him alone, on His Excellency's orders, but I'll be right outside the door. If he's any trouble, just give me a shout." He patted his dagger cheerfully and left. I heard the heavy key grate in the lock.

"Well," I said to Calvus, "What's this all about?"

He half-raised his head. "An . . . n . . .," he managed, in a voice still cracked with thirst.

I knew I would get nothing from him in this state. I let him have the wine-jug. He lifted it two-handed and drank, straight from the lip, in deep grateful gulps. When he had half-emptied it, I took it from him and said, "Well?" again.

He looked at me. "A knife," he gabbled. "It all started with an argument about a knife. I admit that. But it wasn't me who kidnapped him and tied him up . . ."

I interrupted him. "Suppose you start at the beginning, Calvus. Who did you have this argument with, and where?" The butcher heaved a huge sigh. "It was like this . . ." he said, and launched into his tale. It was a long and rambling version of events, but this - effectively - was what he said.

It happened some months earlier, in Corinium. Calvus had gone there to try and buy a slave to help him with his trade. The slave market at Corinium is a lively one, with slaves from all corners of the Empire - much better than the weekly one held in the forum here. So, Calvus left his brother-in-law to mind the stall, hired a mule, and went to Corinium overnight - to another relative who kept an inn. He wanted to be at the market shortly after dawn to get the best choice of slaves available, and perhaps to make some other purchases.

He didn't find a slave to suit, he said, but he was haggling with the vendor of some wool when an itinerant cutler came into the market-place - a dramatic figure, in a multi-coloured robe, with an impressive beard, long hooked nose, and a huge red turban wrapped round his head. I have seen such men in Corinium myself; they come from the North African Province, and their very appearance draws a crowd at once.

This man did. People were already crowding round as he drew a coloured blanket from his handcart, spread it out, and then reverently lifted down a big, carved box.

He didn't open it at once, but stood admiring it, which only made his audience more curious. They jostled closer.

At last, he opened up the front. It hinged apart like a pair of double doors. The watchers gave a gasp. Inside were knives, cleavers, hatchets, every kind of blade. Then, in a high-pitched sing-song kind of voice, he began his cry holding a piece of linen in one hand and running a blade down it so it fell in two. "Best knives. Finest in the Empire. Feel the weight. What do you offer me for these amazing blades? Just like those used by the Emperor himself. Twenty denarii? Fifteen? You won't believe it, gentlemen, I'm asking only five denarii. It is a crime. I'm robbing myself at the price. Only twenty left. Who'll buy the first?"

As Calvus described the scene I could imagine it too well. Five denarii was a fair price for a good knife, and some credulous fool in a tunic was soon pressing forwards, eager to part with his hard-earned coin. Then there was another, and another, until all the knives were gone.

"You bought one of them?" I said.

Calvus shook his head. "Not then. I was still bargaining at the buckle stall. But I was listening all the time. Nicodemus that's what he called himself - sold off the cleavers next. I wanted one of those, but they disappeared more quickly than the knives. Then the hatchets went. By the time I'd finished my business and could get across, there was only one knife remaining in the box. It had a carved bone handle and a wicked blade. He didn't even try to sell us that. Somebody wanted it, but Nicodemus shook his head. That knife was not for sale at all, he said. It was the only one like it in the world, forged in the fires of Vulcan himself."

"You believed that?"

"Of course not, but then he picked it up and started cutting things. It was incredible. I've never seen anything like it in my life, and I've owned scores of knives. Straight through a chicken, bones and all, as if it was a piece of honeycake." Calvus gazed glumly at the stone flagstones on the floor. "I don't know what came over me, but I wanted that knife more than I've ever wanted anything. And Nicodemus knew it. I offered him all the silver in my purse, but he just smiled and shook his head, and made as if to put the knife away."

"So you made him an offer?" I began to see where this might lead.

"A hundred denarii," Calvus admitted.

I gasped. The fact of agreeing on a price - however high made that a contract enforceable in law.

Calvus shuffled his still-shackled feet. "Of course, it was more than I could realistically afford. But I did want that knife. I had the money saved, to buy a slave, but I wasn't carrying it with me in the market-place - it's always full of pickpockets and thieves. I'd left it, hidden in my mule-pack at the inn, where my relatives could keep an eye on it, but where I could get it if I needed it. And I was desperate to have that knife. Perhaps it really was a magic blade. Certainly it put a spell on me."

I thought I could see what was coming next. "But when you went to get the coins he switched the knife?"

Calvus looked at me indignantly. "I am not quite a fool," he said. "Of course I realized that he might do that. But equally he couldn't let me take it till I'd paid. In the end he offered to put it in the box, under my very eyes, and get one of the townsfolk to sit on it - in full view of everyone - until I came back. I couldn't see the flaw in that. I even picked out the bystander - a young man I slightly knew - so there was no possibility of fraud."

"But . . .?" I said. There had to be a but.

"I don't know how he did it to this day, but somehow he played a trick on me!" Calvus groaned. "I got the money: came back: he opened the box and gave me the knife - the only one there was. I was delighted. But when I got back to the inn and went to use the blade - merely to cut a piece of barley-loaf - I knew at once that it was not the same. Oh, it looked identical - ornate carved handle and everything - but it hardly cut. I took it to the ironsmith straight away - his shop is not so very far away - and he tried to grind a decent edge on it - but to no avail. It was just useless, and I'd paid a hundred denarii for it! I've discarded better knives than that!"

I was beginning to feel quite sorry for the man. "So what did you do then?"

"Went back and confronted him, of course - he was still packing up his things - but the crowd had drifted off by then and he just laughed at me. I was not going to put up with that. I called on the aediles, the market police, to have him charged before the magistrates that day."

I nodded. Though a vendor is not liable under the law for the quality of what he sells, a purchaser can sometimes get his money back if he can prove that he was wilfully deceived. "What happened?" I said sympathetically. "Did he avoid arrest?"

That is not unknown. It is the responsibility of the man who brings a case to ensure that both he and the accused appear in person at the town curia before noon on the appointed day, otherwise there's no case to be heard. Not as easy as it sounds, if the accused is reluctant to appear!

Calvus surprised me. He smiled, a little bitterly. "Oh, I'd paid the aediles. It cost me something, naturally, to have it all rushed through like that, but they seized him and dragged him in before the trumpet blew. They made very sure of that."

I could imagine that. The market police are armed, and since they are on the first step to higher things - anxious to be noticed by the authorities for their efficiency. They would ensure that Nicodemus came to court "before the trumpet blew".

That was often the hardest part of all. The Romans have this convention of dividing the hours of daylight into twelve equal parts and calling the resultant divisions "hours" - (and the same thing for the hours of darkness too). But since most of us humbler citizens have no water-clocks, "the start of the seventh hour" is hard to calculate. So, to mark the official middle of the day, a trumpeter comes out onto the courthouse steps and blows - and if you come in after that, you're late. But it seemed that hadn't happened here.

"Did he find some legal quibble, then? Persuade them that they needn't hear the case?"

"On the contrary," Calvus said bitterly, "They heard the case. I lost, that's all."

"But you had witnesses?"

"That was the trouble, in the end. Nicodemus didn't deny the knife was valueless. Instead he turned the whole case on its head. That was the knife that I'd contracted for, he said contracted properly in front of witnesses - 'Do you solemnly swear to buy this knife for one hundred denarii?' - Which, of course, I had. He didn't ask me to swear the contract till I brought the money back. So technically it was that knife that I'd agreed to buy, whatever it was like! The magistrates simply laughed at me and threw me out of court - and I had to pay the aediles all the same. It cost me every coin I possessed."

I frowned. "But you did pay?"

"Of course."

"Then I don't understand. This was months ago. Why are you in prison now?"

He gulped, and I thought for a moment he was going to cry. "This is a much more serious affair. They arrested me today. I'm charged with robbery on a public road. Nicodemus's revenge, I suppose."

No wonder he was looking so distraught. If they found him guilty now, that was a crucifying offence. It cost me the remnants of the wine, which he seemed to require to fortify himself, but in the end I got the story of the day.

Calvus had been at his Glevum market stall, as usual when who should come into the market-place, but Nicodemus, with his box of knives. Calvus was busy with his customers and couldn't leave the stall, but he watched, and it was exactly the same as in Corinium. In no time at all a crowd had formed, and Nicodemus was selling off his knives. Even the patter was identical.

Calvus watched till he could bear no more. The memory of Corinium was still raw. He left his brother-in-law to mind his stall again and made his way to where the cutler was. Nicodemus was selling hatchets by this time - but Calvus noticed there was still a single knife left in the box.

"The same knife?" I interrupted.

"I'm sure of it. The box had been repaired, but the knife looked just the same. I would have known it anywhere - that carved bone handle - it was a work of art. I intended to wait till he began to show it off, and then announce that it was not for sale."

"Because it had been forged in Vulcan's furnaces?"

"Perhaps it was. The way it sliced through everything, it was miraculous. But then someone started bidding for the knife, although the hatchets had not all been sold. The price went up and up, just like before. I don't know what came over me - I was still furious at being made to look a fool. I started shouting that he was a cheat, and people turned to look at me. But the man bidding for the knife was too intent. Then Nicodemus looked up himself. He didn't even recognize my face. It was too much. I strode over and picked up the coloured blanket from the ground, tipped up the box, and sent the whole stand flying." Calvus looked animated, even now, recalling it.

"So he called the aediles, this time?" I suggested.

Calvus shook his head. "He had no need to call them, they were there. And I was ready with my story too - and then Nicodemus realized who I was. And that's when he sprang his next surprise. He claimed that after the trial in Corinium, when he'd won, he'd gone off to the baths to celebrate before he set off for an oppidum, a little village several miles away. But no sooner had he started on the road, than someone came up behind him silently, held a dagger to his ribs and pulled the outer folds of his turban down around his eyes, so that he couldn't see. Then his attacker dragged him off into the trees, stripped him of his purse, pulled off his robes, and left him tied up against a tree. When he came back to his handcart again, he found it had been ransacked, and his knife-box broken into and dashed on the ground."

"It had two compartments, I presume?"

Calvus stared at me. "How did you know that?"

"What other explanation could there be? And what about the knife? The proper knife, that is?"

"He must have had it hidden somewhere else. In any case, it seems it wasn't found. He had it this morning in the market-place, so who knows where it was? But his purse was taken, and he was attacked. And of course, he claims that it was me."

"And was it?"

Under the bruising Calvus turned an ugly shade of puce. "I've been telling them all morning that it wasn't me. I don't have a dagger, anyway. But of course, I'd half-condemned myself by shouting out - in front of everyone in the market-place today - that he'd cheated me in Corinium. And then I turned his knife-stall upside down. That made me seem a violent man. And then he said he recognized my voice."

"Does he have any proof that he was robbed that day?"

Calvus laughed bitterly. "Apparently. A soldier from a passing unit heard his cries - that's how they came and found him stripped and tied up against the tree. The whole detachment thought it was hilarious. No doubt they could be found as witnesses. Oh, Nicodemus was attacked, all right."

I was calculating rapidly. "And what time did you leave Corinium?"

He looked abashed_ "That is the trouble, citizen, I can't be sure. A little after the trial finished I suppose. After I'd spent my money at his stall and paid the fine, there was no point in staying any more. In any case, I'd hired a mule - and I had to return that before the town-gates closed."

"That might be important. Where did you hire the mule?"

He gave me the name. Stortus Maximus. I knew the man. He kept a hiring stable just outside the walls. Most of his animals were old and wheezing - as he was himself - but they were cheap. And Stortus was a decent sort of man. He bought his mules and horses broken-down, but he looked after them - some of them went on for years and years. And he was honest too - the town wags said he lacked the intelligence to cheat.

"Very well," I said. "I'll see what I can do. I'll go and talk to Stortus now. And Calvus, when they question you again, give them the answer but say as little as you can. Otherwise you'll talk yourself to death."

He had turned pale now. "What do you mean?"

I looked at him. "You say you had no dagger, Calvus, but you had a knife. You spent all your money on it, didn't you?"

He looked sullen. "That! It would hardly cut a loaf o' bread."

"But a man could hardly see that from behind. Take my advice, Calvus, watch your tongue. Nicodemus is a cunning man. He'll twist your words, just as he did before. Now, I must go if I'm to save your skin. Guard!"

The warder was opening the door, almost before the word was out. "All right, Citizen? He isn't causing any trouble here?"

I shook my head. "Not at all. But you may show me out and take him to the cells."

From the pathetic look on Calvus's face, he must have hoped I'd somehow contrive to free him then and there. But naturally there was no chance of that. I left him to his miserable lot, and made my way - with some relief - back to the freedom of the world outside.

The soldier at the gate grunted a greeting as he let me out. "There's a message for you from His Excellency. You're to call on him, and tell him how things stand."

"I will," I promised, but I did not go direct. I went first to where Stortus kept his mules.

It was a tumble-down affair, merely a sort of large roofed wooden shed, with a lean-to shack at the back of it. Stortus was with his animals, as usual, giving them fresh water and grooming down their coats, although he stank like a manure-heap himself.