'And then you threw the picture through Hilary's window?'

'I had to get rid of it somehow. That way it looked like a deliberate act of vandalism and hatred and there were plenty of possible suspects for that, not all of them on the headland. It complicated matters even further and it was one more piece of evidence to help Ryan. No one would believe that he would deliberately destroy his own work. But it had a double purpose: I wanted to get into Thyme Cottage. I smashed enough of the window to get through.'

'But that was terribly dangerous. You might have cut yourself, got a sliver of glass on your shoes. And they were your own shoes then; you had disposed of the Bumbles.'

'I examined the soles very thoroughly. And I was particularly careful where I trod. She had left the downstairs lights on so I didn't have to use my torch.'

'But why? What were you looking for? What did you hope to find?'

'Nothing. I wanted to get rid of the belt. I curled it very carefully and put it in the drawer in her bedroom among her other belts, stockings, handkerchiefs, socks.'

'But if the police examined it, it wouldn't have her prints on it.'

'Nor would it have mine. I was still wearing my gloves. Anyway why should they examine it? One would assume that the murderer had used his own belt and had taken it away again. The least likely hiding place for the killer to choose would be the victim's own cottage. That's why I chose it. And even if they did decide to examine every belt and dog lead on the headland I doubt whether they'd get any useful prints from half an inch of leather which dozens of hands must have touched.'

Meg said bitterly: 'You took a lot of trouble to give Ryan an alibi. What about the other innocent suspects? They were all at risk, they still are. Didn't you think of them?'

'I only cared about one other, Alex, and he had the best alibi of all. He would go through security to get into the station and again when he left.'

Meg said: 'I was thinking of Neil Pascoe, Amy, Miles Lessingham, even myself.'

'None of you is a parent responsible for four motherless children. I thought it very unlikely that Lessingham wouldn't be able to provide an alibi and if he couldn't there was no real evidence against him. How could there be? He didn't do it. But I have a feeling that he guesses who did. Lessingham isn't a fool. But even if he knows, he'll never tell. Neil Pascoe and Amy could give each other an alibi and you, my dear Meg, do you really see yourself as a serious suspect?'

'I felt like one. When Rickards was questioning me it was like being back in that staffroom at school, facing those cold accusing faces, knowing I'd already been judged and found guilty, wondering if perhaps I wasn't guilty.'

'The possible distress of innocent suspects, even you, was very low on my list of priorities.'

'And now you'll let them blame the murder on Caroline and Amy, both dead and both innocent?'

'Innocent? Of that, of course. Perhaps you're right and the police will find it convenient to assume they did it, one of them or together in collusion. From Rickards's point of view it's better to have two dead suspects than no arrest. And it can't hurt them now. The dead are beyond harm, the harm they do and the harm that is done to them.'

'But it's wrong and it's unjust.'

'Meg, they are dead. Dead. It can't matter. Injustice is a word and they have passed beyond the power of words. They don't exist. And life is unjust. If you feel called upon to do something about injustice concentrate on injustice to the living. Alex had a right to that job.'

'And Hilary Robarts, hadn't she a right to life? I know that she wasn't likeable, nor even very happy. There's no immediate family to mourn, apparently. She doesn't leave young children. But you've taken from her what no one can ever give back. She didn't deserve to die. Perhaps none of us do, not like that. We don't even hang the Whistler now. We've learned something since Tyburn, since Agnes Poley's burning. Nothing Hilary Robarts did deserved death.'

'I'm not arguing that she deserved to die. It doesn't matter whether she was happy, or childless, or even much use to anyone but herself. What I'm saying is that I wanted her dead.'

'That seems to me so evil that it's beyond my understanding. Alice, what you did was a dreadful sin.'

Alice laughed. The sound was so full-throated, almost happy, as if the amusement were genuine. 'Meg, you continue to astonish me. You use words which are no longer in the general vocabulary, not even in the Church's, so I'm told. The implications of that simple little word are outside my comprehension. But if you want to see this in theological terms, then think of Dietrich Bonhoeffer. He wrote: "We have at times to be willing to be guilty." Well, I'm willing to be guilty.'

'To be guilty, yes. But not to feel guilt. That must make it easier.'

'Oh, but I do feel it. I've been made to feel guilty from childhood. And if at the heart of your being you feel that you've no right even to exist, then one more cause of guilt hardly matters.'

Meg thought, I shall never be able to unlearn, never forget what's happening here this evening. But I have to know the whole of it. Even the most painful knowledge is better than half-knowledge. She said: 'That night I came here to tell you the Copleys were going to their daughter…'

Alice said: 'On the Friday after the dinner party. Thirteen days ago.'

'Is that all? It seems in a different dimension of time. You asked me to come and have supper with you when I got back from Norwich. Was that planned as part of your alibi? Did you use even me?'

Alice looked at her. She said: 'Yes. I'm sorry. You would have been here about half-past nine, just time for me to get back and be ready with a hot meal in the oven.'

'Which you would have cooked earlier in the evening. Safe enough with Alex at the power station, out of the way.'

'That's what I planned. When you declined I didn't press it. That would have looked suspicious later, too like trying to establish an alibi. Besides, you wouldn't have been persuaded to change your mind, would you? You never do. But the very fact of the invitation would have helped. A woman wouldn't normally invite a friend to even an informal supper if she's simultaneously planning a murder.'

'And if I had accepted, if I had turned up here at half-past nine, that would have been awkward, wouldn't it, given your later change of plan? You wouldn't have been able to drive over to Scudder's Cottage to give Ryan Blaney his alibi. And you would have been left in possession of the shoes and the belt.'

'The shoes would have been the greatest problem. I didn't think they'd ever be connected with the crime but I needed to get rid of them before next morning. I couldn't possibly explain my possession of them. I would probably have washed them and hidden them away, hoping for a chance to get them back to the jumble box the next day. Though I would have to have found a way of giving Ryan his alibi. Probably I would have told you that I couldn't get through by telephone and that we ought to drive over at once to tell him that the Whistler was dead. But it's all academic. I didn't worry. You said you wouldn't come and I knew you wouldn't.'

'But I did. Not to supper. But I came.'

'Yes. Why did you, Meg?'

'A feeling of depression after a heavy day, hating seeing the Copleys go, the need to see you. I wasn't looking for a meal. I had an early supper and then walked over the headland.'

But there was something else she needed to ask. She said: 'You knew that Hilary swam after watching the beginning of the main news. I suppose most people knew that who knew that she liked swimming at night. And you were taking trouble to see that Ryan had his alibi for nine fifteen or shortly after. But suppose the body hadn't been discovered until the next day? Surely she wouldn't normally be missed until she didn't turn up at the power station on Monday morning, and then they would telephone to see if she were ill. It might even have been Monday evening before anybody made any inquiries. She could have swum in the morning and not at night.'