Arthur has seen all kinds of death in South Africa, but this is the one he will always remember. A fair fight, open air, and a great cause – he can imagine no better death.

On his return, his patriotic accounts of the war bring approval from the highest ranks of society. It is the interregnum between the old Queen's death and the new King's coronation. He is invited to dine with the future Edward VII and seated beside him. It is made clear that a knighthood is on offer in the Coronation Honours List if Dr Conan Doyle would care to accept it.

But Arthur does not care to. A knighthood is the badge of a provincial city mayor. The big men do not accept such baubles. Imagine Rhodes or Kipling or Chamberlain accepting such a thing. Not that he considers himself their equal; but why should his standards be lower than theirs? A knighthood is the sort of thing fellows like Alfred Austin and Hall Caine grab at – if they are lucky enough to be given the chance.

The Mam is both disbelieving and furious. What has it all been for, if not for this? Here is the boy who blazoned cardboard shields in her Edinburgh kitchen, who was taught each step of his ancestry back to the Plantagenets. Here is the man whose carriage harness bears the family crest, whose hallway celebrates his forebears in stained glass. Here is the boy who was taught the rules of chivalry and the man who practises them, who went to South Africa because of the fighting blood in him – the blood of Percy and Pack, Doyle and Conan. How dare he decline to become a knight of the realm, when his whole life has been aimed towards such a consummation?

The Mam bombards him with letters; to every argument, Arthur has a counter-argument. He insists that they drop the matter. The letters cease; he pronounces himself as relieved as Mafeking. And then she arrives at Undershaw. The whole house knows why she has come, this small, white-capped matriarch who is the more dominant for never raising her voice.

She lets him wait. She does not take him aside and suggest a walk. She does not knock on his study door. She leaves him alone for two days, knowing how the wait will operate on his nerves. Then, on the morning of her departure, she stands in the hallway with the light streaming through the glass escutcheons which shamefully omit the Foleys of Worcestershire, and asks a question.

'Has it not occurred to you that to refuse a knighthood would be an insult to the King?'

'I tell you, I cannot do it. As a matter of principle.'

'Well,' she says, looking up at him with those grey eyes which strip him of years and fame. 'If you wish to show your principles by an insult to the King, no doubt you can't.'

And so, with the week-long Coronation bells still echoing, Arthur is herded into a velvet-roped pen at Buckingham Palace. After the ceremony he finds himself next to Professor – now Sir – Oliver Lodge. They might discuss electromagnetic radiation, or the relative motion of matter and ether, or even their shared admiration for the new monarch. Instead, the two new Edwardian knights talk about telepathy, telekinesis and the reliability of mediums. Sir Oliver is convinced that the physical and the psychical are as close as the shared letters of the two words suggest. Indeed, having recently retired as president of the Physical Society, he is now president of the Psychical Society.

They debate the relative merits of Mrs Piper and Eusapia Paladino, and whether Florence Cook is more than just a skilful fraud. Lodge describes attending the Cambridge sittings, at which Paladino was put through her paces, under strictest conditions, in a sequence of nineteen séances. He has seen her produce ectoplasmic forms; also guitars playing themselves as they float through the air. He has watched a jar full of jonquils being conveyed from a table at the far end of the room, and being held, without any palpable means of support, beneath each of the sitters' noses in turn.

'If I were to play devil's advocate, Sir Oliver, and say that conjurers have offered to reproduce her exploits, and in some cases have succeeded in doing so, how would you reply?'

'I would reply that it is indeed possible that Paladino resorts to trickery on occasion. For instance, there are times when the expectation of the sitters is great and the spirits prove unforthcoming. The temptation is plain. But this does not mean that the spirits which do move through her are not genuine and true.' He pauses. 'You know what they say, Doyle, the scoffers? They say: from the study of protoplasm to the study of ectoplasm. And I reply: then remember all those who did not believe in protoplasm at the time.'

Arthur chuckles. 'And may I ask where you currently stand?'

'Where I stand? I have been researching and experimenting for nearly twenty years now. There is still much work to be done. But I would conclude, on the basis of my findings so far, that it is more than possible – indeed probable – that the mind survives the physical dissolution of the body.'

'You give me great heart.'

'We may soon be able to prove,' continues Lodge with a collusive twinkle, 'that it is not just Mr Sherlock Holmes who is able to escape evident and apparent death.'

Arthur smiles politely. That fellow is going to dog him to the gates of St Peter, or whatever the equivalent turns out to be in the new realm that is slowly being made palpable.

There is little far niente in Arthur's life. He is not a man to spend a summer's afternoon in a deckchair with a hat pulled down over his face, listening to the bees bothering the lupins. He would make as hopeless an invalid as Touie makes a successful one. His objection to inactivity is not so much moral – in his view, the Devil makes work for hands both idle and occupied – as temperamental. His life contains great bouts of mental activity, followed by great bouts of physical activity; in between he fits his social and family life, both of which he takes at a lick. He even sleeps as if it were part of life's business, rather than an interlude from it.

So he has few means of recourse when the machine overstrains itself. He is incapable of recuperating with an idle fortnight on the Italian lakes, or even a few days in the potting shed. He plunges instead into moods of depression and lassitude, which he seeks to hide from Touie and Jean. He shares them only with the Mam.

She suspects that he is more than usually troubled when he proposes a visit on his own account, rather than as a way of making a rendezvous with Jean. Arthur takes the 10.40 from St Pancras to Leeds. In the luncheon car, he finds himself thinking, as he increasingly does, about his father. He now acknowledges the harshness of his youthful judgement; perhaps age, or fame, has made him more forgiving. Or is it that there are times when Arthur feels on the edge of nervous collapse himself, when it seems that the normal human condition is to be on the edge of nervous collapse, and that it is mere good fortune, or some quirk of breeding, that keeps anyone from falling? Perhaps if he did not have his mother's blood in him, he might go – might already have gone – the way of Charles Doyle. And now Arthur begins to realize something for the first time: that the Mam has never criticized her husband, before or since his death. She does not need to, some might say. But even so: she, who always speaks her mind, has never been heard to say ill of the man who caused her so much embarrassment and suffering.

It is still light when he arrives at Ingleton. In the early evening they climb up through Bryan Waller's woodland and emerge on to the moor, gently scattering a few wild ponies. The large, erect, tweeded son aims words down at the red coat and neat white cap of his sure-footed mother. From time to time she picks up sticks for the fire. He finds this habit of hers vexing – as if he could not afford to buy her a cord of the finest firewood whenever she needs it.