“Would you fetch Her Grace the princess for me?” he asks. “I must tell her I cannot ride out with her today.”

“I can tell her myself . . .”

“I want to see her.”

I don’t argue with him, but go down the stairs of his tower, across the hall, and up the stairs of her tower to her rooms and ask her to come to her husband. She is at her morning studies, reading English, frowning over her book. She comes at once, smiling and expectant; her duenna, Doña Elvira, follows with one fierce look at me, as if to ask: What is wrong. What has gone wrong in this cold, wet country now? How have you English failed again?

The princess follows me through Arthur’s great presence chamber, where there are half a dozen men waiting to see the prince. They bow as she goes by and she walks through with a little smile to right and left, a gracious princess. Then she enters into Prince Arthur’s bedroom and the brightness drains from her face.

“Are you ill, my love?” she asks him at once.

He is hunched in his chair at the fireside; my husband, agonized as an anxious hound, stands behind him. Arthur puts out his hand to stop her coming any closer, murmuring so low that I cannot hear what he says. She turns at once to me and her face is shocked.

“Lady Margaret, we must call the prince’s physician.”

“I have sent my servants to find him already.”

“I don’t want a fuss,” Arthur says immediately. From childhood he has hated being ill and being nursed. His brother Harry revels in attention, and loves to be ill and cosseted; but Arthur always swears there is nothing wrong.

There is a tap on the door and a voice calls out: “Dr. Bereworth is here, Your Grace.”

Doña Elvira takes it upon herself to open the door and as the doctor comes in, the princess goes towards him with a ripple of Latin questions too quick for him to understand. He looks to me for help.

“His Grace is unwell,” I say simply. I step back and he sees the prince rise from his chair, staggering with the effort, all color drained from his face. I see the doctor recoil when he sees Arthur, and from his aghast look I instantly know what he is thinking.

The princess speaks urgently to her duenna, who replies in rapid muttered Spanish. Arthur looks from his young bride to his doctor, his eyes hollow, his skin yellowing from one hour to another.

“Come,” I say to the princess, taking her by her arm and leading her out of the bedchamber. “Be patient. Dr. Bereworth is a very good doctor and he has known the prince from childhood. It’s probably nothing to worry about at all. If Dr. Bereworth is concerned, we’ll send for the king’s own physician from London. We’ll soon have him well again.”

Her little face is downcast, but she lets me press her into a window seat in the presence chamber and she turns her head and looks out at the rain. I wave the crowd of petitioners out of the presence chamber and they leave, reluctantly bowing, glancing at the still figure in the window seat.

We wait in silence until the doctor reappears. I can just see as he closes the door that Arthur has returned to his bed and is lying back against the pillows.

“I think he should be left to sleep,” the doctor says.

I go to him. “It’s not the Sweat,” I mutter to him urgently, daring him to contradict me, glancing back at the frozen young woman in the window seat. I realize that I am not asking him for his opinion, I am forbidding him to name our greatest fear. “It’s not the Sweat. It can’t be.”

“Your ladyship, I can’t say.”

He is terrified to say. The Sweat kills within a night and a day, taking the old and the young, the healthy and the frail without distinction. It is the curse that the king trailed behind him when he marched into his kingdom with his army of mercenaries who brought it from the gutters and prisons of Europe. It is Henry Tudor’s blight on the English people, and in the first months after the battle people said that it proved that his line would not prosper; they said that the reign which had begun in labor would end in Sweat. I wonder if this was a prediction laid on our young prince, I wonder if his fragile life is doubly cursed.

“Please God, it’s not the Sweat,” the doctor says.

The princess comes across to him and speaks slowly in Latin, desperate to have his opinion. He assures her that it is nothing more than a fever, that he can administer a draft and the prince’s temperature will come down. He speaks soothingly to her, and goes, leaving me to persuade the princess that she cannot watch over her husband as he sleeps.

“If I leave him now, do you swear to me that you will stay with him, all the time?” she pleads.

“I’ll go back in now, if you will walk outside and then go to your room and read or study or sew.”

“I’ll go!” she says, instantly obedient. “I’ll go to my rooms if you will stay with him.”

The duenna, Doña Elvira, exchanges a level look with me and then follows her charge from the room. I go to the prince’s bedside, conscious that I have now sworn to both his wife and his mother that I will watch over him, but that my watching may be of little use if the young man who is so white and restless in the great curtained bed is the victim of his father’s disease and his mother’s curse.

The day goes by with painful slowness. The princess is obedient to her word and walks in the garden and studies in her rooms and sends every hour to ask how her husband does. I reply that he is resting, that his fever is still high. I don’t tell her that he is getting worse and worse, he is rolling around in feverish dreams, we have sent for the king’s own doctor from London and that I am sponging his forehead, his face, and his chest with wine vinegar and icy water but nothing makes him cool.

Katherine goes to the circular chapel in the courtyard of the castle and prays on her knees for the health of her young husband. Late at night, I look down from the window in Arthur’s tower and I see her bobbing candle in the darkened courtyard and the train of women following her from the chapel to her bedroom. I hope that she can sleep as I turn back to the bed and the boy who is burning up with fever. I put some cleansing salts on the fire and watch the flames burn blue. I take his hand and feel the sweat in his hot palms and his pulse hammering under my fingertips. I don’t know what to do for him. I don’t know what there is to do for him. I fear that there is nothing that anyone can do for him. In the cold long darkness of the night I begin to believe that he will die.

I eat my breakfast in his room but I have no appetite. He is wandering in his mind and will neither eat nor drink. I have the grooms of the bedchamber hold him while I force the cup against his mouth and pour small ale down his throat until he chokes and splutters and swallows, and then they lie him back on the pillow and he throws himself around in the bed, hot, and getting hotter.

The princess comes to the door of his presence chamber and they send for me. “I shall see him! You will not prevent me!”

I close the door behind me and confront her white-faced determination. Her eyes are shadowed like bruised violets; she has not slept all night. “It may be a grave illness,” I say, not naming the greatest fear. “I cannot allow you to go to him. I should be failing in my duty if I let you go to him.”

“Your duty is to me!” shouts the daughter of Isabella of Spain, driven to rage by her fear.

“My duty is to England,” I say to her quietly. “And if you are carrying a Tudor heir in your belly, then my duty is to that child as well as to you. I cannot allow you to go closer than to the foot of the bed.”

At once she almost collapses. “Let me go in,” she pleads. “Please, Lady Margaret, just let me see him. I will stop where you say, I will do as you command, but for Our Lady’s sake, let me see him.”

I take her in, past the waiting crowds who call out a blessing, past the trestle table where the doctor has set up a small cabinet with herbs and oils and leeches crawling in a jar, through the double doors to the bedroom where Arthur is lying, still and quiet, on the bed. He opens his dark eyes as she comes in, and the first words he whispers are, “I love you. Don’t come closer.”

She takes hold of the carved post at the foot of the bed, as if to stop herself from climbing in beside him. “I love you too,” she says breathlessly. “You will be well?”

He just shakes his head and, in that terrible moment, I know that I have failed in my promise to his mother. I said that I would keep him safe, and I have not. From a wintry sky, from an east wind—who knows how?—he has taken the curse of his father’s disease, and My Lady the King’s Mother will be punished by the curse of the two queens. She will pay for what she did to their boys, and see her grandson buried and, no doubt, her son also. I step forward and take hold of the princess by her slight waist and draw her to the door.

“I shall come back,” she calls to him as she takes unwilling steps away from him. “Stay with me; I will not fail you.”

All day we fight for him, as arduously if we were infantrymen bogged down in the mud of Bosworth Field. We put scalding plasters on his chest, we put leeches on his legs, we sponge his face with icy water, we put a warming pan under his back. As he lies there, white as a marble saint, we torment him with every cure that we can think of, and still he sweats as if he is on fire, and nothing breaks his fever.

The princess comes back to him as she promised to do and this time we tell her that it is the Sweat and she may go no closer to him than the threshold of his room. She says that she has to speak with him privately, orders us all from the room and stands on tiptoe, holding the doorjamb, calling across the herb-strewn floor to him. I hear a quick exchange of vows. He asks for a promise from her, she agrees but begs him to get well. I take her arm.

“For his own good,” I say. “You have to leave him.”

He has raised himself up on one elbow and I catch a glimpse of his deathly determined face. “Promise,” he says to her. “Please. For my sake. Promise me now, beloved.”