If they are to proceed with the act for which she has been paid, for which she has accepted payment, she must overcome her present embarrassment and move on to the next step. She has been forewarned of his bad leg, of his untrustworthy undercarriage in general. Since he would find it hard to straddle a woman, it would be best if she were to straddle him. While she is negotiating that passage, he will have problems of his own to wrestle with, problems of quite another order. Perhaps, among the blind, there grow up intuitions of beauty based solely on touch. In the realm of the unseen, however, he is still groping his way. Beauty without the sight of beauty is not yet, to him, imaginable. The episode in the lift, during which his attention was held as much by the old woman as by her, has left behind in his memory only the sketchiest of outlines. When to a wide-brimmed hat, dark glasses, the curve of an averted face he tries to add heavy breasts and spreading, unnaturally soft buttocks, like volumes of liquid trapped in silk balloons, he cannot make the parts cohere. How can he even be sure they belong to the same woman?

Gently he tries to draw the woman to him. Though not resisting, she turns her face away, either because she is unwilling to yield her lips or because she does not want to give him a chance to lift off her glasses and explore what lies beneath – does not want it because where mutilation is concerned men are notoriously queasy.

How long since she lost her sight? Can he decently ask? And can he then decently go on to the next question: Has she been loved since it happened? Is it experience that has taught her her devastated eyes will kill off a man's desire?

Eros. Why does the sight of the beautiful call eros into life? Why does the spectacle of the hideous strangle desire? Does intercourse with the beautiful elevate us, make better people of us, or is it by embracing the diseased, the mutilated, the repulsive that we improve ourselves? What questions! Is that why the Costello woman has brought the two of them together: not for the vulgar comedy of a man and a woman with parts of their bodies missing doing their best to interlock, but in order that, once the sexual business has been got out of the way, they can hold a philosophy class, lying in each other's arms discoursing about beauty, love, and goodness?

And somehow or other, in the midst of all of this – the fretting, the embarrassment, the averting, the philosophising, to say nothing of an attempt on his part to loosen his tie, which has begun to choke him (why on earth is he wearing a tie?) – somehow, clumsily yet not as clumsily as might have been, shamefacedly yet not so shamefacedly as to paralyse them, they manage to slip into it, into the physical act to which they have willy-nilly contracted themselves, an act which while not the act of sex as generally understood is nevertheless an act of sex, and which, despite the truncated haunch on the one hand and the blasted eyes on the other, proceeds with some dispatch from beginning to middle to end, that is to say in all its natural parts.

What disquieted him most in Costello's account of Marianna was what she said about the hunger or thirst raging in her body. He has never been fond of immoderacy, immodesty, wild motions, grunts and shouts and cries. But Marianna seems to know how to contain herself. Whatever is going on inside her she keeps to herself; and, once they have concluded, she swiftly makes everything decent again, more or less. The sole intimation he has of either raging thirst or raging hunger comes in the form of an unusual but not unpleasing heat at the core of her body, as though her womb or perhaps her heart were glowing with a fire of its own.

Though the sofa was built neither for sexual coupling nor for subsequent philosophic languor, and though, without a covering, they are soon going to be chilled, there is no question yet of groping their way to a proper bed in a proper bedroom.

'Marianna,' he says, testing the name on his tongue, tasting the two ns: 'I know that is your name, but is it what people call you? There isn't another name you use?'

'Marianna. That is it. That is all.'

'Very well,' he says. 'Marianna, Mrs Costello says we have met before. When was that?'

'A long time ago. You took my photograph. It was for my birthday. You don't remember?'

'I don't and can't remember because I don't know what you look like. And it can't be that you remember me because you don't know what I look like. Where did it take place, this portrait session?'

'In your studio.'

'And where was the studio?'

She is silent. 'It is too long ago,' she says at last. 'I can't remember.'

'On the other hand, our paths did cross much more recently. We shared a lift at the Royal Hospital. An elevator. Did Mrs Costello mention that?'

'Yes.'

'What else did she say?'

'Just that you were lonely.'

'Lonely. How interesting. Mrs Costello is a close friend of yours?'

'No, not close.'

'What then?'

There is a long silence. He strokes her through her clothes, up and down, thigh, side, breast. What a pleasure, and how unexpected, to have the freedom of a woman's body again, even if the woman is invisible!

'Did she just walk in on you?' he says. 'She just walked in on me.'

He feels her shake her head slowly from side to side.

'Does she intend, do you think, that you and I should become a couple? For her entertainment perhaps? The halt leading the blind?'

The remark is meant lightly, but he can feel her stiffen. He hears the lips part, hears her swallow, and all of a sudden she is crying.

'I am sorry,' he says. He reaches out to touch her cheek. It is bathed in wetness. At least, he thinks, she has tear ducts left. 'I am sorry, truly. But we are grown people, so why are we letting someone we barely know dictate our lives? That is what I ask myself.'

She gives a gasp that is presumably a laugh, and the laugh brings on sobs. She sits up beside him, half dressed, sobbing freely, shaking her head from side to side. Now is surely the time to slip off the blindfold, wipe the muck from his eyes, behold her as she is. But he does not. He waits. He tarries. He delays.

She blows her nose on a tissue she seems to have brought with her, clears her throat. 'I thought,' she says, 'this was what you wanted.'

'It is, make no mistake about it, it is. Nevertheless, the idea came from our friend Elizabeth. The first impulse. She issues instructions, we follow. Even when there is no one to see that we obey.'

See. Not the right word, but he lets it stand. She must be used to it by now, to people who say 'see' when they mean something else.

'Unless,' he goes on, 'she is still in the room, observing, checking up.'

'No,' Marianna says, 'there is no one here.'

There is no one here. Being blind, and therefore attuned to the subtler emanations of living beings, she must be right. Nevertheless, the feeling has not left him that he need only reach down and his fingers will encounter Elizabeth Costello, stretched out on the carpet like a dog, watching and waiting.

'Our friend advocated this' – he waves a vague hand – 'because in her eyes it represents the crossing of a threshold. She is of the opinion that until I have crossed a certain threshold I am caught in limbo, unable to grow. That is the hypothesis she is testing out in my case. She probably has another hypothesis to cover you.'

Even as he speaks he knows it is a lie. Elizabeth Costello has never used the word growth in his hearing. Growth comes out of the self-help manuals. God knows what Elizabeth Costello really wants, for him or for herself or for this Marianna; God knows to what theory of life or love she really holds; God knows what will happen next.

'Anyway, having crossed her threshold, we are now free to proceed to higher and better things.'