'But it is significant, Paul, truly it is! You know, there are those whom I call the chthonic, the ones who stand with their feet planted in their native earth; and then there are the butterflies, creatures of light and air, temporary residents, alighting here, alighting there. You claim to be a butterfly, you want to be a butterfly; but then one day you have a fall, a calamitous fall, you come crashing down to earth; and when you pick yourself up you find you can no longer fly like an ethereal being, you cannot even walk, you are nothing but a lump of all too solid flesh. Surely a lesson presents itself, one to which you cannot be blind and deaf

'Really. A lesson. With a little ingenuity, it seems to me, Mrs Costello, one can torture a lesson out of the most haphazard sequence of events. Are you trying to tell me that God had some plan in mind when he struck me down on Magill Road and turned me into a hobbler? What about yourself? You told me you have a heart condition. Interpret your heart condition to me. What lesson did God have in mind when he struck you in the heart?'

'It is true, Paul, I do indeed have a heart condition, I was not telling a fib. But I am not the only one so afflicted. You have a heart condition of your own – do you really not know that? When I came knocking at your door, it was not to find out how a man rides a bicycle with one leg. I came to find out what happens when a man of sixty engages his heart unsuitably. And, if you don't mind my saying so, you have been a sorry let-down thus far.'

He shrugs. 'I was not put on this earth to entertain you. If you want entertainment' – he waves a hand at the runners, the cyclists, the good folk taking their dogs for a walk – 'you have a wide range to explore. Why waste your time on someone who exasperates you with his obtuseness and keeps letting you down? Give me up as a bad job. Visit yourself on some other candidate.'

She turns and bestows on him a smile that lacks, as far as he can see, any malice. 'I may be capricious, Paul,' she says, 'but not as capricious as that. Capricious: goat-like, leaping from one rock to another. I am too old for leaping. You are my rock. I will stay with you, for the time being. As I told you – remember? – love is a fixation.'

He shrugs again. Love is a fixation. One might equally well call love a bolt of lightning that strikes where it wills. If he is an ignorant baby when it comes to the maladies of love, he does not see that the Costello woman is any better. But he is not going to argue with her. He is tired of arguing.

He is also thirsty. A cup of tea would go down very well. They could cross the bridge to the tea-room on the other bank. They could go back to the flat with its noise and disorder. Or they could forget about tea and go on dawdling here by the riverside, letting the afternoon pass, watching the waterfowl disport themselves. Which?

'Tell me about your marriage,' says Elizabeth Costello. 'You hardly ever mention your wife.'

'I think not,' he says. 'It would not be proper. My wife would not thank me for offering her up as a minor character in one of your literary efforts. But if it is stories you want, I will tell you a story from the period of my marriage that does not involve my wife. You can use it to illustrate my character, or not, as you wish.'

'All right. Shoot.'

'It comes from the time I was still running the studio in Unley. I had two assistants, and one of them happened to fall in love with me. To be accurate, it was not love but adoration. She had no designs on me. That was why she could be so open about it. A perfectly intelligent girl. Pretty too. A fresh-faced, pretty, twenty-year-old girl in a solid, sturdy body, the body of a rugby player. Nothing she could do about it. No diet was going to save her, transfigure her into a sylph.

'I was teaching an evening course at the time, at what used to be the polytechnic. Principles of photography. Three evenings a week this girl came to my class. Sat in the back row and gazed at me. Took no notes.

' "Don't you think this is becoming excessive, Ellen?" I said to her. "It's my only chance," she replied. No blushes. She never blushed. "Your only chance for what?" "To be alone with you." That was how she defined being alone with me: being free to sit in class and watch and listen.

'I had a rule: never get involved with employees. But in this one case I had a lapse. I broke the rule. I left a note for her: a time, a place, nothing else. She came, and I took her to bed.

'You probably expect me to say it was a humiliating experience, for her and therefore for me. But it wasn't humiliating at all. I would go so far as to call it joyous. And I learned a lesson from it: that love need not be reciprocated as long as there is enough of it in the room. This girl had enough love for two. You are the writer, the heart expert, but did you know that? If you love deeply enough, it is not necessary to be loved back.'

The Costello woman is silent.

'She thanked me. She lay in my arms crying and gasping "Thank you, thank you, thank you!" "It's all right," I said. "No need for anyone to thank anyone."

'The next day there was a note on my desk: "Whenever you have need of me…" But I did not call on her again, did not try to repeat the experience. Once was enough, to absorb that lesson.

'She worked for me for another two years, keeping a correct distance because that was what I seemed to want. No tears, no reproaches. Then she disappeared. Not a word, just stopped coming to work. I spoke to her colleague, my other assistant, but she was in the dark. I telephoned her mother. Didn't I know, the mother said? Ellen had taken a new job and moved to Brisbane as a rep for a pharmaceuticals company. Hadn't she given notice? No, I said, this was the first I heard of it. Oh, said the mother, she told us she had spoken to you and you were quite cut up.'

'And?'

'That's all. End of story. I was quite cut up: aside from the lesson in love, that was the part that interested me most. Because I wasn't cut up, not at all. Did the girl really think I would be cut up because she had left my employ? Or was the story about her boss being cut up just something she told her mother so that she would not seem too abject?'

'Are you asking my opinion? I don't know the answer, Paul. The claim that you, her boss, were cut up may be the part of the story that you find interesting, but it is not what interests me. What interests me is the Thank you, thank you! Is Thank you, thank you! what you plan to say to Marijana if and when she yields herself to you? Why didn't you say Thank you, thank you! to the girl I procured for you, the one you singled out for your attentions because she would not be able to witness you in your sadly reduced state?'

'I did not single her out. You were the one who brought her up.'

'Nonsense. I merely took my cue from you. You singled her out in the hospital lift. You had dreams about her. Why did you not thank her, I repeat? Was it because you paid her, and if you pay you don't need to say thank you? Your rugby player had enough love for two, you say. Do you really think love can be measured? Do you think love comes by volume, like beer? That as long as you bring a case of it, the other party is permitted to come empty-handed – empty-handed, empty-hearted? Thank you, Marijana (Marijana with the j this time), for letting me love you. Thank you for letting me love your children. Thank you for letting me give you my money. Are you really such a dummy?'

He stiffens. 'You asked me for a story, I gave you a story. I am sorry you don't like it. You say you want to hear stories, I offer you stories, and I get back nothing except ridicule and scorn. What kind of exchange is that?'

'What kind of love?, you might have added. I didn't say I didn't like your story. I found it interesting, and well told too, the story of you and your rugby player. Even the interpretation you give is interesting in its own right. But the question that nags me is: Why does he pick on this story to tell me, this above all others?'