I looked round for a seat where I could sit, myself, but there was nothing in the room except a little clothes-chest with an oil-lamp on top and the straw mattress where Paulina was. I leaned against the wall. ‘Tell me how Lavinia escaped the lodging-house. Did she really climb through the window-space, as she just did here? When I first realized that she hadn’t run away, I thought the cloth-rope through the window was a ruse, intended to mislead.’

Secunda gave the smile that would excuse her anything. ‘You are quite right, citizen. The nursemaid made it and put it there (having made sure that there was no one watching in the court, of course) but not until her daughter had safely gone. We had taken Lavinia with us – she was hidden in the travelling box, asleep.’

I frowned. ‘But I thought you had your so-called slave-boy with you when you went? Several people mentioned seeing him – though nobody recognized him as the Lavinia they knew.’

‘That was not Lavinia, of course. That was a pauper’s child that we had hired for just an hour or two. His parents were delighted when we wanted him. We kept him with us till we were out of town, then let him go again and sent him home. He could not believe his luck. But by that time Lavinia was beginning to wake up.’

‘But how . . . ?’ I was about to say, and then I understood. ‘She had been given the sleeping-potion in the phial. Of course!’ I have never had a child, but I can imagine that it would be hard to keep Lavinia quiet and still if she had been awake. ‘Cyra provided the potion for you, I suppose? I noticed her seal-mark on the wax seal of the flask. Though at that time I was more interested in the hemlock that the jug had obviously contained.’

‘Hemlock? In the flask?’ She sounded quite surprised. ‘Then the nursemaid must have put it there. Certainly there was no hemlock in it earlier.’

‘But there was hemlock somewhere. That’s what killed Lavinia’s mother and she drank it from the flask.’ I stopped lounging on the wall and pushed myself upright. Paulina glanced up at me and gave me a huge smile, then moved a little and patted the space that she had made.

I squatted down beside her, thinking how bizarre it was to be talking of such things, while this child was totally oblivious of all the tragedy. She was engrossed in drawing something now, something with sticks which might have been a tree. I looked up at Secunda, not unhappy to be sitting at her feet.

‘There was some hemlock left from what my husband gave the Druid girl,’ she was saying, thoughtfully. ‘It was still with her effects. The nursemaid asked to keep it, “just in case of an emergency”, she said, though at the time we hoped that everything was going to go to plan. She gave the sleeping potion to Lavinia and it worked beautifully.’

I was still trying to get a picture of events. ‘It must have been a strong one.’

‘Very strong indeed. Cyra warned us not to use the whole of it. I think the mother only used a half, but even that much had a fast effect, because when Paulinus and I got back from the slave-market, the child was sound asleep. Her mother had cut her hair off, while she slept, and put her in the half-empty box that we had left behind.’

‘I found a hair or two,’ I said. ‘I didn’t find a razor or a knife.’

‘We put it in the box beside Lavinia, together with the hair. We had thought of selling it to a wig-maker – hair of that length and colour would fetch a handsome price – but we decided it might cause remark. So we put that in there too. We covered her loosely with a rug that we had brought, and pulled the lid down – Paulinus had deliberately chosen one that didn’t fit, so that it stayed a little bit ajar – and he personally carried down the box and put it on the cart. And we drove off with it. It went off more smoothly than we dared to hope.’

I was aware of something tugging at my sleeve. I looked down. It was Paulina wanting to show me what she’d scratched onto the slate. A big head and fingers had sprouted on the tree – I realized it was meant to be a person. Was it me? I pointed to myself and she nodded gleefully, then took it from me and went back to work, blissfully unaware of the amazing story that was unfolding here.

I looked at Secunda. ‘So all that time the nurse was apparently on guard outside the room, Lavinia wasn’t there at all?’

‘Of course not citizen, that was the whole idea. The nurse was to wait until she heard the noonday trumpet sound, then go down for the tray – as if Lavinia had just requested it. There were deliberately quite a lot of items to be brought upstairs, so many that she could not carry up the tray alone. That way someone from the lodging-house would be a witness when she knocked the door, and – when there was no answer – help her to burst in and so raise the alarm. Though Lavinia had been gone for hours by then, of course.’

I was marvelling at the beautiful simplicity of this. ‘And she even took the poison afterwards to put us off the scent?’

Secunda shook her head. ‘That was not originally part of the plan at all. The idea was for the nurse to go out into the town – allegedly searching for the missing girl – and, following our directions, find her way out here. But she did not come. By this morning we were anxious, as you may suppose. When you arrived we thought it might be to bring us news of her. Which in a way you did.’ She sighed. ‘Something must have gone dreadfully amiss.’

‘It did,’ I told her. ‘The landlady at the lodging house was naturally afraid that she and her household would be held responsible for Lavinia’s escape. She decided (quite correctly as it now appears) that the nursemaid must have had a hand in it, so she had her locked up in the kiln-house in the yard – I think you know the place – and sent word to Lavinius to come and take her home and beat the truth from her.’

‘As no doubt he would have done,’ Secunda murmured. ‘I wish we’d thought of the possibility of suspicion falling on the nurse – I think we all believed that she loved the girl so much that nobody could possibly have thought she was involved. But from what you say it’s clear now why she chose to kill herself. She obviously feared that she would not be strong enough to withstand questioning without betraying us. Lavinius can be ruthless. He’d have tortured the poor creature horribly if he thought that she knew anything at all.’

‘Even though by that time he’d disowned the girl?’

‘It is evident that you don’t know Lavinius, citizen. Anyone who caused dishonour to his precious family name would be punished without mercy – you can take that from me. No wonder the poor woman chose to drink the hemlock-juice and die an easy death. There may have been some of the sleeping-potion in the phial as well, which would have eased it further. I only hope there was. I’m glad that she had the foresight to take it to the kiln.’

I shook my head, remembering the look of hope that crossed the nurse’s face when she thought that I had come from Cyra, not from Publius. I knew now that she was hoping that this might be a subterfuge and that I had come to help her to escape. Poor creature, she was disappointed there. ‘That was my doing, inadvertently. She persuaded us that there was something in the room that might help her to discover where Lavinia was. Only of course there was no clue at all. It was the poison that she wanted. She almost told me so.’ (I remembered suddenly the last thing that the nurse had said to me, ‘If I can tell you nothing in the morning, citizen, do as you like with me.’ Those words had taken on another meaning now.) ‘After she’d drunk the hemlock she threw the flask away – I think in one last attempt to create a mystery and persuade us that Druids were involved in that event as well.’

I had hardly finished speaking when the bedroom door burst open and Paulinus rushed in – now dressed in his faded tunic and his working-boots again. His face was ashen and his air of gentle bafflement had given way to something more like terror and despair.

‘Wife!’ he murmured, swaying on the spot. ‘So everything is lost! I’ve spoken to Lavinia and she says the secret’s out and Lavinius’s servants are waiting in the barn. What are we to do?’

She was on her feet in an instant and rushing to his side. If she had not supported him by giving him her arm, I believe that he would have crumpled to the floor. I too had scrambled to my feet by now and I went over to assist her. Between us we held him upright by the door while Paulina gazed up at us in astonishment, chewing at her chalk.

How long we might have stood there I cannot say, but then Muta came hobbling into the ante-room from the yard outside – obviously her master had rushed ahead of her, and with her limping gait she had not kept up with him. She came to take my place supporting Paulinus but Secunda signalled her to stay there with the child. Muta looked doubtful, but nodded dutifully.

We left the maid admiring the portrait of the tree, while – between us – we led Paulinus next door to a stool and helped him to lower his body onto it.

He sat there for a moment, his head between his hands. After a little he looked up at me and I saw to my embarrassment that his lids were fringed with tears. It is a rare thing to see a Roman adult cry, even women tend to save their tears for funerals and for a male to weep in public is regarded as disgrace.

It was evident that Paulinus did not care a sugared fig for any such convention. He said to me in a voice which had lost all trace of joy, ‘So it is all over. You have found us out. Why did you come here? Life could have been so good! Does it give you satisfaction to have ruined it? And why? Just to satisfy your curiosity?’

I found myself pacing up and down the room, not knowing how on earth to answer this. I stopped before the household altar in the wall, seeing the simple sacrifices that had been offered there to the household spirits and the goddess of the hearth. I felt a sudden fury with these Roman deities. Why had they not ensured that I had left the house before Modesta and the other slaves arrived?

I turned to Paulinus. ‘I have decided that I need not tell anyone about Lavinia,’ I said.

To my surprise this did not seem to comfort him.

It was Secunda who broke the awkward silence first. ‘Husband, the citizen deserves more courtesy. I have told him the whole truth about Lavinia’s parentage – he had very largely worked it out in any case. Don’t you think that we should thank him for not betraying her?’ Her voice was entirely serene, but I thought I detected a warning tone in it.

Paulinus seemed to sense it too. He raised his head again. ‘Of course, but what about the rest of it? I couldn’t bear to be without you, after all we’ve been through and everything we’ve planned.’ He looked from her to me and his face took on that faintly puzzled air. ‘Or hasn’t he discovered the whole truth of it?’

She put an arm around his shoulder, gently, rather as a mother might console a child. ‘Not until this moment, husband, I don’t think. And none of it from me.’

I was frankly baffled for a moment, though I should not have been. Of course there was still a mystery to solve. Publius had employed me to try to find his bride, but then we had found her body in the box and I’d come on to Corinium to investigate. I still had no idea how that had come about. But I had been so occupied with the discovery of the truth about Lavinia that I had not turned my mind to the other matter recently.

Now though, as a result of what Paulinus said, I was forced to think again. It was becoming obvious that these two were involved in that grisly business with the corpse. My heart rebelled against the notion, but my brain refused to let the matter rest.

I turned to Paulinus, who was on his feet by now and staring at his wife with a look of dawning horror on his face. ‘You were involved in putting that body in the box?’

He looked at Secunda as if for some support, but she shook her head at him. ‘Tell him, Paulinus. There’s no help for it. If he asked the question, we shall have to tell the truth. But since he’s shown compassion for Lavinia, perhaps we can persuade him to do the same for us.’

I was about to insist upon his answering but he was too quick for me. He spoke before I had time to formulate my thoughts. ‘Will you promise, citizen? Can we rely on that? You will not betray us either?’ He reached out and slowly interlaced his fingers with his wife’s – or rather . . . ?

I must have been baffled by her loveliness, or the obvious solution would have dawned on me before.

‘Great Mars!’ I said, hardly able to believe the words myself. ‘You are not his wife at all!’