Hayes woke to red light in the viewport and a left hand that already knew how to make a fist.
That was the trick of it. He sat up, scratched his jaw, poured the clear ration into a cup, and only noticed the graft when the band on that wrist lit with Smith's order.
Sandbox. Now.
The dining hall was empty. The corridors were empty. Base One still sounded like a building waiting on a war that had not clocked in.
Smith stood in the middle of the sandbox with his hands behind his back. The room had no far wall again. The floor was blank stone until he spoke.
"Mining hull. Dark. Limited rounds. You do not look for anyone who is not in the brief."
The stone became plated deck. Blood in the seams, but clean enough to be a lie. A rack rose: short rifle, cutter, a bar that could pin a hatch.
Hayes took the rifle with his right hand out of habit. The left found the forend without being asked. Weight sat where weight should sit. No lag. No argument.
The lights died.
He moved.
A body in the passage. A wet sound deeper in. A hatch yawning. He did not fire. He barred the hatch with the steel rod and kept going down, not back, the way the settlement had taught him: first scream is not always the job.
The thing on the other side hit the metal. The shock ran up the bar and into the graft. The hand closed harder on its own, correcting grip before he told it to.
Hayes almost said good to a piece of himself.
Lights up.
Smith did not praise him.
"You forgot the arm."
"It didn't give me a reason to remember."
"That is the point of K's work. It is also the danger. A tool you forget is a tool you will ask to do something a bone should not." Smith flicked the room. The corridor became a ladder well, then a cargo net over a drop, then a narrow crawl with a jammed panel. "Again. Use both hands like they were born on you. When the room punishes you, I want to know which hand paid."
They ran it until Hayes's shirt stuck to his back.
On the crawl, a lip of metal bit his left palm. He hissed, shook it, and looked—expecting torn skin. The plate had scuffed. No blood. The pain was real and then it was information: pressure, heat, a clean edge.
He flexed the fingers. They answered like they always had.
That was when it landed. Not in the surgery. Here. He had climbed, braced, barred, and fired a dry snap on a drill target without once thinking this is not mine.
Smith saw the look.
"Do not get romantic about it. Eat. K wants you in the hangar annex."
Dr. K had claimed a metal table and covered it in things that did not belong on an arm: collars, plates, a slim blade housing, a palm disk, a lattice that looked like jewelry if jewelry came out of a weapons locker.
"Sit. Sleeve up. Don't flex until I say."
Hayes sat. K turned the forearm in the light and rapped a knuckle on the inner plate. A seam answered with a faint click Hayes had never noticed.
"You feel whole because the map is whole," K said. "That does not mean the hardware is finished. Official medical gives you a hand and a smile. I give you a dock. The dock is why Smith lets me land here."
He set the first piece in Hayes's palm. A smooth disk, warm.
"Magnetic plate. Cargo, hull, rifle if you drop one like an idiot. Low draw. Won't hold a ship. Will hold you to a wall if the gravity cuts."
Hayes pressed it to the table on instinct. It bit. He had to peel it free with his right hand.
"You didn't tell it to do that," K said. "The interface guessed. Good. Also illegal on a white-wing ward. Don't demonstrate in the fleet."
Second piece: a knuckle housing.
"Impact. Not a punch that wins wars. A punch that opens a jammed dog. Overuse it and the dock heats. You will feel that as toothache in a hand that does not have teeth. Listen when it complains."
Third: a tool collar that seated just above the wrist, thin enough to hide under a cuff.
"Driver, cutter bit, probe. Engineering would weep. You are not yellow. You do not get their toys. You get the version that does not look like a workshop."
Hayes turned the collar. A probe slid out of the index like a fingernail deciding to be useful.
He laughed once, short, surprised at himself.
K did not.
"Last one for today." A darker plate, ribbed. "Recoil brace. Ties the graft to a weapon's kick so the shoulder does not eat it alone. Your old double-barrel would have loved this. Your new rifles will assume it."
Hayes looked at the spread.
"All of it at once?"
"No. The dock holds two without the map getting noisy. Three if you like headaches and bad dreams that are not Ronos. We start magnet and brace. The rest stay in the case until the sandbox says you earned the weight."
He fitted the magnet into the palm until it seated with a sound Hayes felt in his teeth. The brace locked along the ulna line. For a second the arm was other—cold, extra, a stranger shaking hands from the inside.
Then the map swallowed it.
Hayes opened and closed the fist. Same hand. Same self. Only the table now stuck to him when he wanted it to.
"Forgot again," K said, watching his face. "Good. Come back tomorrow. If the dream changes shape—if the giant starts chewing metal instead of meat—you tell me. That means the new pieces are writing on the old pain. I can work with that. I cannot work with you lying that you slept fine."
Hayes nodded.
On the walk back he sent Lilith four words because Smith had banned speeches.
Training. Arm still mine.
Her reply landed before he reached the bunk.
Good. Don't break it. Yellow is loud.
He lay down and made a fist in the dark. Magnet whispered against magnet in the casing. The dream came later, same teeth, same forearm—but when Ronos bit, the mouth hit plate and sparked.
Hayes woke with the left hand already closed, already his, and for a long breath he could not remember which arm the giant had taken first.