He came up out of black water with his mouth full of sand.
It was cold. That was the first thing, before he knew where he was or how. A November cold, brown and heavy, pulling at his coat, and under his feet not stone but something soft that gave. He stood up. The water came to his waist. He was holding the astrolabe against his chest so hard the rim had cut into his palm.
Grey dawn. A wide, slow river. On the far bank, a long line of houses with their backs to the water, washing hung from poles, shutters still closed. Upstream, a bridge on low stone piers with little buildings standing on it, crowded together like teeth. And behind it all, above the roofs, a great red dome with a white lantern on top, catching the first of the light.
He knew that dome. He'd had it on a postcard over his bed in Camden Town since he was twelve. His mother had sent it from her sister's in Lucca, the summer before the war.
Florence.
Then the fever hit him, and the river came up to meet his face again.
* * *
The woman who pulled him out was called Bice, and her husband was a renaiolo, one of the men who dug sand out of the bed of the Arno with long-handled scoops and sold it to the builders by the boatload. They had a hut of planks and reeds on the gravel below the walls, by the Porta San Niccolò, and a brazier, and a pot, and four children who stood in a row in the doorway and stared at John for two days while he lay under a sheep's fleece and shook.
He'd been ill before. Trench fever, at Armentières, in 1917. This was like that, but faster, and stranger. His teeth chattered and his skin burned, and when he shut his eyes he saw the glass city by the sea, and a paper cup with lipstick on its lid, and a wooden pier at Brighton with a straw hat going end over end along the boards.
Clara. Edmund, get it.
He hadn't been to Brighton since he was six.
On the second evening the fever broke, and he sat up, and Bice gave him a bowl of bread soup with black cabbage in it, and he ate three bowls and could have eaten five.
"Ciao," he said to the smallest child, when he'd finished, because it was what his mother said to children.
The child looked at him blankly. So did Bice.
"Where are you from?" said Bice. "You talk like a priest from Lucca who's been hit on the head."
"Lucca," said John, which was half true. "And then a long way north."
"Hm," said Bice. She looked at his jacket, drying by the brazier. Good grey worsted, from a tailor in Tottenham Court Road, two years old. She looked at his boots, which had steel toecaps and laces with metal tips. "Very far north."
He paid her with a collar stud. It was rolled gold and worth about fourpence in 1920, and she bit it and looked at him as if he'd given her a ring. Her husband, Nencio, who had not said a word in two days, gave him a dead brother's hose and doublet and a brown wool cloak in exchange for the grey jacket. John kept the trousers on under the hose. He kept the boots. He kept his wristwatch where it was, under his shirt cuff, and the wallet with his brother's letter in the inside of his doublet, and the astrolabe wrapped in a rag in the bag Bice gave him.
"Where are you going, Lucca?" said Bice, at the door of the hut, on the morning of the fourth of November.
"To find a painter."
She laughed. "Throw a stone."
* * *
He didn't need to throw a stone. He'd read the books. In October 1503 the Signoria had given Leonardo da Vinci the keys to a great hall at the convent of Santa Maria Novella, the Sala del Papa, so that he could draw a battle on a cartoon the size of a wall. John had seen the date in a footnote at the British Museum. He walked there through streets that smelled of woodsmoke and horse dung and the tanneries by the river, past men unloading barrels from carts, past a bakery with its door open and the heat rolling out, past a chapel where a priest was saying mass to six old women and a dog. Twice he stopped and stood still because the doubled pictures came back: a cart that hadn't yet turned a corner, a boy who hadn't yet dropped his basket. Twice it passed. His head ached.
The convent was huge and green and white, with a long front of striped marble. A friar with a broom told him the painter was upstairs, round by the great cloister, and that if he was a creditor he should get in line.
He was halfway up the stone stairs when he heard the crash.
* * *
The Sala del Papa was a long, high hall with tall windows down one side, and it was full of paper.
Paper on trestles. Paper pinned to boards. Paper on the floor in drifts, sketches of horses' heads and men's faces with their mouths open, and in the middle of the room a wooden scaffold with ropes and pulleys that held up an enormous sheet, pieced together from dozens of smaller ones, on which a battle was beginning in charcoal: horses rearing, men tangled together around a standard, every face a shout.
A trestle had gone over. Inkpots on the floor, a bowl of red chalk spilled across the tiles like blood.
By the scaffold stood an old man in a rose-coloured tunic that came only to his knees, with a long grey beard and long grey hair, holding a leather roll of papers against his chest with both arms.
In front of him, a younger man with a knife.
He was about twenty-five and lean, with a broken nose and a soldier's leather jerkin, and he held the knife low and point up, the way men held them who had used one. He hadn't seen John. He was talking, quietly and quickly, in an accent that wasn't Florentine.
"...don't care about your horses, old man. I care about the roll. The fortresses. Imola, Cesena, Faenza. All of them. You drew them for him. Now you'll give them to me."
"I drew them for the Duke Valentino," said the old man. His voice was light, almost interested. "Who is, I hear, in Rome and not well. If he wants his maps he may come and ask for them. You, my friend, may go and drown."
"I'll take them from you dead."
"Then you'll get them with a great deal of blood on them, and they'll be very hard to read."
The knife came up.
John didn't think. He was across the hall before he'd decided to be, and as the young man turned at the sound of his boots on the tiles, John pushed.
The hall slowed.
He saw everything. He saw the knife turning towards him, the light running along its edge. He saw the young man's weight going onto his front foot, his shoulder dropping, the line the blade would take: low, under the ribs, the way they'd taught it with bayonets at Étaples. He saw it clearly enough to draw it on a blackboard. He had all the time in the world to see it.
He did not have all the time in the world to move.
His body was a twenty-four-year-old physicist's body that had been sitting in a laboratory for three years, and it moved the way it always had, which was not very fast. He got his left arm across. Not far enough. The blade went into his forearm above the wrist, through the wool, through the skin, and opened it, and he felt it as a line of white cold and then as heat.
The world came back at full speed.
The young man was very close, surprised, his face a foot from John's. John did what he'd learned in a trench at Messines from a sergeant from Glasgow who'd never read a book: he grabbed the knife wrist with his right hand and held it, and drove his forehead into the bridge of that broken nose, and as the man reeled back brought his knee up between his legs as hard as he could.
The man made a sound like a kicked dog and went down on one knee. The knife clattered on the tiles.
John put his boot on it.
They looked at each other. The young man was bleeding from the nose. So was John. Then the young man was on his feet and gone, through a side door, his steps rattling away down a back stair, and the door banged, and somewhere below a friar shouted.
John stood in the spilled red chalk with his arm running blood onto the floor, and shook.
* * *
"Sit," said Leonardo da Vinci. "No, not there, there's a wet cartoon. Here. On the bench. Hold your arm up. Higher. Above your heart, the blood is lazy, it doesn't like to climb. Good."
He bound it himself, with strips torn from a linen sheet, quickly and tightly and very well. His hands were large and spotted and absolutely steady. He smelled of linseed oil and charcoal and something sweet, like aniseed. He didn't speak while he worked. When he'd tied the last knot he sat back on his heels and looked up at John, and his eyes were pale grey and very bright and missed nothing.
"You moved," he said, "before he did."
John said nothing.
"Not quickly. You're not quick. I've seen quick men. Cesare's Spaniards are quick, they'd have had your liver out." Leonardo tilted his head. "But you knew. You turned your arm into the blade before the blade had decided where to go. As if you'd seen it already. And your nose began to bleed. Before he hit you. I watched it." He held up one finger, smudged black. "And your hands. Give me your hand."
John gave it to him. Leonardo held it between both of his.
"Cold," he said. "Cold as a dead man's. In a room with a brazier." He let go. "Who are you?"
It would be easy. It would take a moment. He could feel where the last few minutes sat in the old man's head, the knife, the boots on the tiles, the nosebleed. He could find the joins and take the strip away and leave Leonardo blinking by the scaffold with a bloody bandage he didn't remember tying.
And something would come with it. Some piece of Leonardo da Vinci, the way Clara Hartley had come with the pencil and the sandwiches. He'd carry it for the rest of his life, and Leonardo would wake at night from a dream of a stranger in a brown cloak, and never know why.
Not again. Not this soon.
"My name is John," he said. "Giovanni, here. I've come a very long way."
"From where?"
"London."
"I've met Englishmen. They don't fight with their heads." Leonardo was watching him. "How long a way?"
John looked at the battle on the wall. The horses. The men with their mouths open.
"About four hundred and seventeen years," he said.
He waited for the laugh, or the friar's shout, or the sign of the cross.
Leonardo da Vinci didn't laugh. He looked at John for a long moment, and then he got up and went to a trestle and came back with a notebook, small, bound in red leather, and a stick of chalk, and sat down on the floor at John's feet like a boy.
"Good," he said. "Start at the beginning. Speak slowly. And if you're lying, lie well. I hate a dull liar."
* * *
It was dark when Salai came in, a beautiful sulky young man with curls, carrying a basket of bread and a dead hare, and found his master on the floor in the chalk with half a notebook filled and a bloodstained stranger on the bench.
"What happened?" said Salai.
"A thief," said Leonardo, without looking up. "This gentleman saw him off. He's staying." He turned a page. "Salai, what did the thief drop?"
Salai bent and picked something up from under the scaffold. A small leather purse on a broken thong. He weighed it in his hand, and his face showed, for a moment, a deep professional interest, before he handed it over.
Leonardo opened it. A few silver coins. A twist of paper with salt in it. And a little disc of red sealing wax, of the kind a man carried to prove who had sent him.
He held it to the candle.
Pressed into the wax was a bull. A small, stocky, charging bull.
Leonardo went very still.
"Then it isn't my horses he wanted," he said quietly. "Or my maps." He closed his hand on the wax. "It's Cesare's. And whoever's left of Cesare's men in Florence knows where I sleep."