Jason noticed the change one morning a few weeks after the first game of chess, lying on his back on the leaves with the gray light coming in through the cave mouth.
For years, his first thought on waking had always been the same. Another one. Another day to get through, another stick to push into the sand, another stretch of hours to fill until he could sleep again. It had been waiting for him every single morning, before he even opened his eye, as reliable as the tide.
This morning, his first thought had been: What did he do with the good rope?
He lay there for a while, turning that over. Then he sat up and looked across the cold fire pit at Alexander, who was asleep face down on his side of the cave with one arm flung over his head and the good rope, for reasons Jason couldn't begin to guess, tied around his ankle.
Jason laughed out loud, and woke him up.
* * *
"Your knots are terrible," Alexander said later that morning, once he had untangled himself. He was holding up the vine rope Jason had braided years ago for the pond, frowning at it as if it had personally offended him. "Honestly. How has anything on this island stayed tied?"
"It held my whole weight."
"By accident." Alexander undid it in two quick movements that Jason didn't even see, and held out the loose end. "Sit down. I'm fixing this."
"You're fixing me?"
"I'm fixing your knots. You're beyond help."
Jason sat. Alexander sat down across from him on the warm rock at the mouth of the cave, took the rope back, and held it up between them.
"This is the first one every ship's boy learns," he said. "Watch."
His hands moved. There was a loop, and a twist, and the end of the rope went up through the loop and around behind and down again, and then Alexander pulled, and there was a knot in the rope that had not been there a moment before. The whole thing took perhaps two seconds.
"Again," Jason said. "Slower."
Alexander did it again, slower. Jason watched his fingers with his whole attention, the way he used to watch a professor's hands at the whiteboard when the equation was about to turn into something important. Loop. Twist. Up through the loop, around the back, down again.
"Now you."
Jason took the rope. He made the loop. He made the twist. He brought the end up through the loop, and around the back, and down again, and pulled.
The whole thing fell apart in his hands.
Alexander made a small noise that he probably thought was a cough.
"Don't," Jason said.
"I didn't say anything."
"You were going to."
"I was going to say," Alexander said, with enormous dignity, "that the rabbit goes around the tree, not through it."
Jason stared at him. "The what?"
"The rabbit. The end of the rope. It comes up out of the hole, runs around the tree, and goes back down the hole." Alexander took the rope and showed him again, very slowly, narrating as he went. "Out of the hole. Around the tree. Back down the hole. That's how they teach it to the boys. There's a bosun on my father's flagship who has been shouting about that rabbit for thirty years."
"That's ridiculous."
"It works."
Jason tried again. Out of the hole, around the tree, back down the hole. He pulled, and this time the knot held.
He turned it over in his fingers and frowned at it. It was a neat, small, tight thing, and he could see that it would hold, but he couldn't see why. The rope was just rope. There was nothing locking it in place.
"Why doesn't it slip?" he asked.
Alexander blinked. "What?"
"When you pull on it. The loop stays the same size. Why doesn't the rope just slide through?"
"Because it's a bowline," Alexander said, as if that explained everything. When Jason kept looking at him, he shrugged. "I don't know. It just doesn't. Nobody ever told me why. They just told me to tie it."
Jason looked at the knot for a long moment. Then he loosened it a little, and pulled on the standing end, and watched which parts of the rope moved and which parts didn't.
"It's friction," he said slowly. "Look. When you pull here, this part squeezes down on the end, right here, where it goes around. The harder you pull, the harder it squeezes. So it holds tighter the more weight you put on it. But this part never takes any load, so if you push it back the other way..." He pushed. The knot opened like a flower. "It comes apart."
He looked up. Alexander was staring at him.
"What?" Jason said.
"Nothing." Alexander took the knot from him and pulled on it, and pushed it back, and watched it open, and his face slowly changed. "I've tied that knot ten thousand times. I never once thought about why it worked."
"That's the only thing I know how to do," Jason said. "Think about why things work."
"Well." Alexander handed the rope back to him. "Then I'll teach you how, and you can tell me why, and between the two of us we'll be the finest sailor who ever lived."
It went on like that all morning.
Alexander showed him a knot that held tighter the harder you pulled, and one that came undone with a single tug, and one that joined two ropes of different thicknesses so that neither could slip away from the other. Jason tied each one badly, then less badly, then right, and each time he took it apart again and worked out where the grip was and where the weight went, and explained it out loud, and Alexander listened with his head tilted to one side like a bird.
Then Alexander showed him the mast knot.
"This one's for storms," he said. His voice had changed a little, grown quieter. "You tie it around a man's chest and around the mast, and then the sea can have the ship if it wants, but it can't have him. It's saved more sailors than any surgeon in the Republic."
Jason took the rope, and found that his hands had gone still.
He was thinking about the raft. About the night of the storm, the ropes he had tied himself with, the ones that hadn't held. The wave coming down out of the dark. The whole world turning over, and nothing, nothing at all, to hold on to.
If he had known this knot then, he might still have had the raft.
He might never have reached the island.
He sat there with the rope in his hands, and didn't move, and after a moment he realized Alexander wasn't talking anymore either. Alexander was just waiting. He didn't ask what was wrong. He didn't say anything at all. He only sat there on the warm rock with his hands on his knees and let the silence be as long as it needed to be, the way he had on the night of the cliff.
After a while, Jason breathed out.
"Show me again," he said. "Slowly."
Alexander showed him. Jason tied it. It was wrong. He tied it again, and it was wrong again, and the third time, it held.
Alexander took the knotted rope, looped the free end around the trunk of the stunted tree beside the cave, leaned back into it with his full weight, and hung there at an angle over the rocks, grinning.
"Well?" Jason said.
"It holds," Alexander said. "The bosun would have kept you." He hauled himself back upright.
"Have you ever used it?" Jason asked.
"Once. On my first voyage." Alexander paused. "I tied it wrong. The bosun had to cut me loose before I strangled myself."
Jason looked at him.
"I was fourteen," Alexander said with great dignity. "Again. Faster this time."
After that, they practiced every morning. By the end of the first week, Jason could tie most of the knots with his eyes closed, and his fingers ached every night, and he could explain every single one of them.
* * *
The knots were only the beginning.
Over the months that followed, Alexander taught him everything a boy learned in his first years at sea. He taught him to read the weather, and made him guess it every morning, and kept score on a flat stone by the fire; Jason lost for the whole first season. He taught him to hold his breath the way the pearl divers of the Outer Isles did, slowly and calmly, because the first need to breathe was a lie and there was always more air left than it told you. Jason came up gasping after forty seconds the first time. By the end of the season he could lie on the bottom of the lagoon for nearly three minutes, watching the light move on the surface far above him, and not be afraid.
And every evening before sunset, Alexander handed him a stick and hit him with his own until one of them yelled. It was nearly always Jason, and nearly always from the right, where he couldn't see it coming. "Anyone who actually wants to hurt you," Alexander told him, "won't be polite enough to attack your good side. So keep your blind side to a wall, and make them come around to where you can see them." By the end of the summer, Jason had learned to put his back to the old fruit tree and turn his head, and the first time he landed a blow on Alexander's shoulder, Alexander grinned as if he'd been given a present.
In return, Jason taught him to build. They made better traps, and a wall of woven branches across the cave mouth to keep out the wind, and a stone oven that Jason was absurdly proud of. And, biggest of all, they made the cistern: a basin dug into the stone floor near the cave mouth, lined with clay carried in armfuls from the stream bed across the plain, and fed by a network of bark gutters running down from the rocks above. It took them a month. Then they waited for rain.
* * *
The storm came in the middle of the afternoon, rolling in off the sea in a long gray wall, and they sat side by side at the mouth of the cave to watch it.
The first drops hit the rocks above them. Then the rain came properly, hammering down on the cliff, and for a long, terrible moment nothing happened at all. Jason sat very still, staring at the empty basin, running every calculation again in his head. The angle of the gutters. The seal on the clay. The—
Water came trickling down the first gutter, hesitated at the joint, and spilled over into the second. Then it was running, all of it at once, a dozen thin streams pouring off the rocks and down the bark channels and into the basin, where it began, slowly, to pool.
Alexander let out a whoop that echoed off the cave walls.
They watched it rise for an hour. Neither of them could look away. The water crept up the clay sides a finger's width at a time, clear and cold and utterly still beneath the rain, and every so often one of them would get up to adjust a gutter that didn't need adjusting, just to be closer to it.
"I've stood on the deck of a warship with three hundred men," Alexander said eventually, "and I have never been as proud of anything as I am of that hole."
Jason laughed. Then, because the rain showed no sign of stopping and there was nothing else to do, Alexander smoothed a patch of ash by the fire and started drawing in it with a stick.
It was a ship. Not the little escort he had served on, but one of the great warships of the Republic, the kind his father commanded. He drew the long steel hull and the funnels, and then, when Jason leaned over to look, he drew it again from the side, cut open like a diagram, and started explaining. The boiler rooms deep in the belly of the ship, where the stokers worked stripped to the waist in the heat. The coal bunkers. The gun decks, and the officers' cabins at the stern with their brass lamps. And the galley, right in the middle, where the cooks fed three hundred men a day out of iron pots the size of barrels.
"The whole crew eats from the same pots," Alexander said. "Officers and all. My father insists on it. He says a crew that eats the same food fights the same war."
"Why are you teaching me all this?" Jason asked. "I'm never going to set foot on one."
Alexander shrugged. "Because you asked what they were like, and I can't stop talking."
Jason reached for the knife to trim a new stick for the fire, the way he did every evening. His hand closed on bare stone.
He looked down. The stone by the fire, the one where the knife lived, was empty.
"Alexander," he said, very calmly. "Where's the knife?"
Alexander opened his mouth. Then he closed it again, and a look of dawning horror spread across his face, and he turned his head slowly toward the rain.
"The lagoon," he said. "I was cleaning fish this morning. I must have—"
Jason was already on his feet.
He went out into the storm without a word, and after a moment he heard Alexander splashing after him. The rain was coming down so hard that he could barely see the path. By the time they reached the lagoon, the water had risen over the rocks where Alexander had been sitting that morning, and the waves were slapping at the edge of the sand, and for a long, sick minute Jason couldn't see anything at all.
Then Alexander dropped to his knees in the shallows and started digging with both hands, and came up holding the knife, streaming with water, half-buried in the wet sand where the tide had almost taken it.
They stood there in the rain, soaked to the skin, looking at it.
"It's the only knife we have," Jason said. His voice was shaking, and he couldn't tell whether it was from cold or anger. "It's the only knife on this entire island. Do you understand that? If the tide had come in an hour earlier—"
"It didn't."
"It could have!"
Alexander wiped the rain out of his eyes and grinned at him. "You sound exactly like my first captain."
"Was he right?"
"Always," Alexander said. "It was infuriating."
He held out the knife, handle first. Jason took it. They walked back up the path in silence, and when they reached the cave, Alexander took the knife from him again, set it very carefully on its stone by the fire, and patted it.
"There," he said. "Home. Happy?"
Jason was not happy. He had spent four years building a routine that had kept him alive, and every day Alexander strolled straight through the middle of it, like a man through a spiderweb, without noticing. He was soaked and cold and still angry, and water was dripping off the end of his nose.
But the cistern was full to the brim beside him, and Alexander was standing there dripping and grinning, and Jason found that he was, somehow, laughing.
* * *
Months later, on his way back from checking the fish traps, Jason passed the line of sticks along the top of the beach.
He hadn't looked at them properly in a long time. He stopped now and looked at the long gray row running away toward the far end of the sand, and at the place where it ended.
He had stopped putting them in the ground because each one had meant another day to survive, and there had come a morning when he couldn't face adding one more. He hadn't planted one since. And he realized, standing there with the wind in his hair, that he hadn't even thought about it in weeks. He didn't know what day it was, or how many had passed since the fever, or since Alexander had washed up on the rocks. He had been too busy to count. The days had been too full of knots and storms and chess and arguments about where the knife belonged.
Up at the cave, Alexander was shouting something about a bird.
Jason looked at the empty sand beyond the last stick, and for the first time in years, it didn't frighten him.
He left the sticks where they were, and went back up to see about the bird.