Six did not wait for an order.
The crab walked into the current, straight up the slope, and planted himself between the boulder and the Heartstone.
He dug all eight legs into the rock.
He lowered his body and raised both claws, the old one and the new one.
The boulder hit him.
Mav felt it as if it had struck his own chest.
Six was rank E-.
He was three times as strong as the crab that had once bent a metal bar.
He used Stone Shell, and his whole body turned as hard as rock.
He caught the boulder with both claws, and for a moment, it stopped.
Then it began to move again.
It was too heavy, and the Churn was pushing behind it.
Six slid backward.
His legs cut eight long grooves in the rock.
His new shell cracked, from one side to the other, with a sound Mav felt in his teeth.
Six did not let go.
‘He can’t hold it alone.’
Mav looked desperately at what he had.
He had a harpoon.
He had one free hand, and two sprouts on his arm.
Eight, Nine and Ten could not leave their cracks without being swept away.
Two and Five were gone.
That left Seven.
She was the strongest of them all.
She was four meters of muscle, and she was lying 10 meters away, outside what was left of the wall.
But the boulder was coming for the Heartstone.
To stop it, she would have to come right up against the stone.
For her, that meant going blind.
It meant swimming into a noise so loud that it wiped out every other sense she had.
She had never done it.
Not once, in all the nights she had circled this place.
Not even after Seven took her.
Mav could have ordered her.
He was almost sure she would obey.
He remembered Five, trembling in front of him, on the day he had said GO.
‘No.
Not like that.’
He reached for the cold river in his head, and he did not push.
‘Seven.
I need you.
The stone is going to break.
If it breaks, we all die.
Would you be willing to help us, please?’
For a moment, nothing happened.
Then the long pale shape rose off the seabed.
She came through the mud like a spear.
He felt the instant she crossed into the hum of the Heartstone, because her whole mind went white.
She could not feel the water.
She could not feel the boulder.
She could not feel him.
But she kept coming.
He guided her.
It was all he could do.
He showed her where Six was and where the boulder was, the way he would have led a blind man by the hand.
‘Left.
More.
There.
Now push!’
Seven threw her body against the boulder beside Six.
She wrapped herself around the lower half of it and braced her tail against the seabed.
Six heaved from the front.
The boulder shook.
It stopped.
It had stopped an arm’s length from the Heartstone.
Relief flooded through Mav.
Mav let out a breath he did not need.
Then he untied the cord, pushed himself along the rock on his knees, and jammed the shaft of his harpoon under the boulder, as deep as it would go.
The metal bent.
He piled stones around it, one after another, with his one free hand, until the gap was full.
‘It won’t hold forever.
It only has to hold until this ends.’
He crawled back to the Heartstone, tied himself to it again, and put his body between the stone and the boulder.
If it moved again, it would have to go through him first.
It was a stupid place to sit.
He knew that.
He was not strong enough to stop it.
He sat there anyway.
There was no other choice.
The Churn lasted the whole day.
Mav did not remember most of it afterward.
He remembered being cold.
He remembered the taste of mud.
He remembered Eleven and Twelve, wrapped around his arm, two small bright points against his chest that he checked every few minutes.
He remembered talking to them.
It was not orders.
It was the kind of thing a person says to a frightened child.
‘It’s all right.
It’ll stop soon.’
At some point, Ten’s root gave way.
The seaweed came sliding past his leg, and he pinned it under his knee and kept it there for hours, until his leg went numb.
At some point, the crack in Six’s shell began to close.
Mav saw the green thread run along it, from one side to the other, while the crab stood with both claws locked on the boulder.
Regeneration was slow, but it was enough to keep him in one piece.
All day long, Seven stayed where she was.
She stayed inside the hum, blind and deaf, with her body wrapped around a rock she could not feel.
Mav could sense what it cost her.
It was like standing next to a furnace with her eyes shut.
Every part of her wanted to flee.
But she did not flee.
She had been his for six days.
Before that, she had spent eight days trying to eat him.
Mav felt a gratitude that he did not know how to express.
‘I won’t forget this.’
It ended at dusk, as suddenly as it had begun.
The roar grew quieter.
The stones stopped hitting his back.
The current, which had been tearing at them since dawn, became a pull, then a push, then nothing.
The groan under the seabed faded away.
The water was still brown.
He could not see his own hand in front of his face.
But it was not moving anymore.
Mav untied the cord with fingers that would not bend.
He tried to stand, and found that he could not.
He sat back down in the mud.
The base was gone.
He did not need to see it to know that.
There was no wall, no larder and no dens.
Weeks of work had been carried off down the slope.
The Heartstone was still beating against his back.
‘It’s whole.
I’m alive.
That’s what’s important.
The rest comes after.’
He closed his eyes and looked at the points in his head.
Six.
Seven.
Eight and Nine, bent but rooted.
Ten, under his knee.
Eleven and Twelve, on his arm.
And One, in his own neck, quiet and cool.
That made eight.
He had 10 Subjects.
He searched for the other two.
He searched in every direction, as far as he could reach.
There was nothing.
‘Two.
Five.
Answer me.’
The water was silent.
Mav sat in the dark, with his heart beating very fast, and started to worry about his two missing Subjects.