Cordelia asked:

'But how could she do it, how could she bear to be there with you in the house, watching you with her husbands-knowing that you were going to have his child?'

'She did it because she loved Ronald and couldn't bear to lose him. She hadn't been much success as a woman. If she lost her husband, what else was there for her? She couldn't have gone back to her father. Besides, we had a bribe for her. She was to have the child. If she refused, then Ronald would leave her and seek a divorce to marry me.'

'I would rather have left him and gone off to scrub doorsteps.'

'Not everyone has a talent for scrubbing doorsteps and not everyone has your capacity for moral indignation. Evelyn was religious. She was, therefore, practised in self-deception. She convinced herself that what we were doing was best for the child.'

'And her father? Didn't he ever suspect?'

'He despised her for her piety. He always had. Psychologically he could hardly indulge that dislike and at the same time think her capable of deceit. Besides, he desperately needed that grandchild. It wouldn't have entered his mind that the child might not be hers. And he had a doctor's report. After our third visit to Italy we told Dr Sartori that Mrs Callender's father was concerned about her care. At our request he wrote a reassuring medical report on the progress of the pregnancy. We went to Florence together a fortnight before the baby was due and stayed there until Mark arrived. Luckily he was a day or two before time. We'd had the foresight to put back the expected date of delivery so that it genuinely looked as if Evelyn had been caught unexpectedly by a premature birth. Dr Sartori did what was necessary with perfect competence and the three of us came home with the baby and a birth certificate in the right name.'

Cordelia said:

'And nine months later Mrs Callender was dead.'

'He didn't kill her, if that's what you're thinking. He wasn't really the monster that you imagine, at least, not then. But in a sense we did both destroy her. She should have had a specialist, certainly a better doctor than that incompetent fool Gladwin. But the three of us were desperately afraid that an efficient doctor would know that she hadn't borne a child. She was as worried as we were. She insisted that no other doctor be consulted. She had grown to love the baby, you see. So she died and was cremated and we thought we were safe for ever.'

'She left Mark a note before she died, nothing but a scribbled hieroglyphic in her prayer book. She left him her blood group.'

'We knew that the blood groups were a danger. Ronald took blood from the three of us and made the necessary tests. But after she was dead even that worry ended.'

There was a long silence. Cordelia could see a little group of tourists moving down the path towards the bridge. Miss Learning said:

'The irony of it is that Ronald never really loved him. Mark's grandfather adored him; there was no difficulty there. He left half his fortune to Evelyn and it came automatically to her husband. Mark was to get the other half on his twenty-fifth birthday. But Ronald never cared for his son. He found that he couldn't love him, and I wasn't allowed to. I watched him grow up and go to school. But I wasn't allowed to love him. I used to knit him endless jerseys. It was almost an obsession. The patterns got more intricate and the wool thicker as he grew older. Poor Mark, he must have thought that I was mad, this strange discontented woman whom his father couldn't do without but wouldn't marry.'

'There are one or two of the jerseys at the cottage. What would you like me to do with his things?'

'Take them away and give them to anyone who needs them. Unless you think I ought to unpick the wool and knit it up into something new? Would that be a suitable gesture, do you think, symbolic of wasted effort, pathos, futility?'

'I'll find a use for them. And his books?'

'Get rid of them too. I can't go again to the cottage. Get rid of everything if you will.'

The little group of tourists was very close now but they seemed engrossed in their own chatter. Miss Learning took an envelope out of her pocket and handed it to Cordelia.

'I've written out a brief confession. There's nothing in it about Mark, nothing about how he died or what you discovered. It's just a brief statement that I shot Ronald Callender immediately after you had left Garforth House and coerced you into supporting my story. You'd better put it somewhere safe. One day you may need it.'

Cordelia saw that the envelope was addressed to herself. She didn't open it. She said:

'It's too late now. If you regret what we did, you should have spoken earlier. The case is closed, now.'

'I've no regrets. I'm glad that we acted as we did. But the case may not be over yet.'

'But it is over! The inquest has given its verdict.'

'Ronald had a number of very powerful friends. They have influence and, periodically, they like to exercise it if only to prove that they still have it.'

'But they can't get this case reopened! It practically takes an act of parliament to change a coroner's verdict.'

'I don't say that they'll try to do that. But they may ask questions. They may have what they describe as a quiet word in the right ear. And the right ears are usually available. That's how they work. That's the sort of people they are.'

Cordelia said suddenly:

'Have you a light?'

Without question or protest Miss Learning opened her handbag and handed over an elegant silver tube. Cordelia didn't smoke and was unused to lighters. It took three clicks before the wick burst into flame. Then she leaned over the parapet of the bridge and set fire to the corner of the envelope.

The incandescent flame was invisible in the stronger light of the sun. All Cordelia could see was a narrow band of wavering purple light as the flame bit into the paper and the charred edges widened and grew. The pungent smell of burning was wafted away on the breeze. As soon as the flame tinged her fingers, Cordelia dropped the envelope, still burning, and watched it twist and turn as it floated down small and frail as a snowflake to be lost at last in the Cam. She said:

'Your lover shot himself. That is all that either of us need to remember now or ever.'

They didn't speak again about Ronald Callender's death, but walked silently along the elm-lined path towards the Backs. At one point Miss Learning glanced at Cordelia and said in a tone of angry petulance:

'You look surprisingly well!'

Cordelia supposed that this brief outburst was the resentment of the middle-aged at the resilience of the young which could so quickly recover from physical disaster. It had only taken one night of long and deep sleep to return her to the state which Bernie, with irritating coyness, used to describe as bright eyed and bushy tailed. Even without the benison of a hot bath the broken skin on her shoulders and back had healed cleanly. Physically, the events of the last fortnight had left her unscathed. She wasn't so sure about Miss Learning. The sleek platinum hair was still swathed and shaped immaculately to the bones of the head; she still carried her clothes with cool distinction as if it were important to appear the competent and unharassed helpmate of a famous man. But the pale skin was now tinged with grey; her eyes were deeply shadowed, and the incipient lines at the side of the mouth and across the forehead had deepened so that the face, for the first time, looked old and strained.

They passed through King's Gate and turned to the right. Cordelia had found a place and had parked the Mini within a few yards of the gate; Miss Learning's Rover was further down Queen's Road. She shook hands firmly but briefly with Cordelia and said goodbye as unemotionally as if they were Cambridge acquaintances, parting with unusual formality after an unexpected meeting at Evensong. She didn't smile. Cordelia watched the tall, angular figure striding down the path under the trees towards John's Gate. She didn't look back. Cordelia wondered when, if ever, they would see each other again. It was difficult to believe that they had met only on four occasions. They had nothing in common except their sex, although Cordelia had realized during the days following Ronald Callender's murder the strength of that female allegiance. As Miss Learning herself had said, they didn't even like each other. Yet each held the other's safety in her hands. There were moments when their secret almost horrified Cordelia by its immensity. But these were few and would get fewer. Time would inevitably diminish its importance. Life would go on. Neither of them would ever forget completely while the brain cells still lived, but she could believe that a day might come when they would glimpse each other across a theatre or restaurant or be borne unprotestingly past on an underground escalator and would wonder whether what they both recalled in the shock of recognition had really once happened. Already, only four days after the inquest, Ronald Callender's murder was beginning to take its place in the landscape of the past.