Luke was curled in a tiny terrified ball the day Vader came to retrieve him. When he heard his father coming he ran to the bars at the front of the cell, praying that Vader would stop at his cell to say something to him. At this point he would have taken anything, even words of hatred, just to have Vader acknowledge him.
Vader stepped into his son's cell and motioned to the troopers outside. Two of them had slung Luke over their shoulders before they realized that it would be easier for one of them to carry him. Vader groaned inwardly at his useless guard.
Luke moaned softly and reached out to his father. Vader turned from the boy and started off back to his shuttle. Soon the galaxy will free of that scum and I will have my angel back. This is about to end. With Luke gone and Padmé back I won't need Palpatine anymore. With Padmé to protect I can find the strength to destroy that disgusting corpse.
With this happy thought Vader boarded his shuttle. Luke was carried up and into the cargo hold. Vader could hear soft sobs as the boy was carried past him. You`re a loyal little boy, aren`t you? I bet you thought that it would make me love you. You were wrong, stupid boy. Your sick devotion won't help you. Although I hear you have been begging for death, so I suppose in a way it will. Vader considered sending these thoughts to his son but he decided that the boy could wait to be let down.
Luke curled up in his new cell and tried to convince himself that his father was trying to avoid having the troopers learn that he did care about his son. If he hates me as much as he says, why did he get me out of jail? He must have changed his mind about me. He has to love me. I need him to love me. What kind of parent would treat me the way he does? He must be acting. Luke clung to these thoughts as he felt the ship start to move.
Up in the cockpit, Vader was lost in thoughts of his own. Are you ready, Angel? We'll be together again soon. Everything is finally coming back together. I will finally destroy the Jedi and we can rule the galaxy together, the way it was meant to be. The time is coming now. I have the last Jedi and he is the key to having you again.
In his cell, Luke reached out through the Force to his father, Father, are you there? No answer. The ship bumped and Luke hit his head on the floor. He sat up, holding his head, and stared at the door, waiting for one of the troopers to come for him.
He got a pleasant surprise when it was Vader who opened the door.
"Dad!" Luke jumped to his feet and raced to his father, forgetting that it was only safe to call Vader that in his daydreams.
Stupid boy, you will learn your place soon enough; if you live long enough to. Vader picked his son up and started up to his castle with the boy in his arms. Luke clung to his father's neck in blind trust.
Vader entered a lift and pressed the button for the top floor. Luke released his father's neck as the lift started to move. Vader placed him on the floor and let him lean on the wall of the lift.
"Thank you, Father. I was starting to worry that you didn't care." Luke moved away from the wall to press close against his father.
"So it's true. You really are smarter than you look."
Luke recoiled at his father's words, "What do you mean? If you don't want me back why did you go back for me?"
"Or maybe you really are a stupid farm boy." The lift jerked to a halt, "I never wanted you," the door opened, and Vader gestured to a strange machine, "I wanted her."
The machine looked like it had been homebuilt, it resembled a chair attached to a torture frame, and both had needles and sensors hanging off of them. On the chair sat a beautiful woman in a long, flowing dress. She was unconscious and hooked up to the strange machine. Luke had a bad feeling about who would be attached to the torture frame.
His fears were confirmed as Vader walked over to it and turned back to him, "Come here, Boy."
Luke stumbled backwards and mumbled, "My name is Luke Skywalker."
"Your name is not important. Get over here."
"My name is important to me. I had hoped that it might be special to you." Luke started to inch into a corner, as far away from his father as possible.
Vader sighed, "I had hoped that you might make this easy for me. Don't you want to make Daddy happy?" he mocked.
Tears were rolling down Luke's cheeks, "I do! I'm just scared that that'll mean that you're going to hurt me."
"I am going to hurt you, whether you do as I ask or not."
"At least tell me why you're doing this to me. Who is she?" Luke waved his arm at the woman.
"How sad it must be, not to recognize your own mother. Her name is Padmé. What I'm doing to you will bring her back to me. It's fitting, you are the reason she is dead, and you will be the reason that she returns to me."
"Clearly this is going to hurt me, but will it hurt her?"
"It will not. She will not be happy about your death but she will be physically unharmed. Come here and I will explain as we go along."
My death. He talks about his only son dying like its tomorrow's weather. Why? What did I do wrong? Luke stumbled towards his father, "If it's going to kill me I want to kiss Mom goodbye."
Luke stepped up onto the platform the chair sat on and he looked at his mother's face for the first time. Mom, is this what you would want? Would you be willing to see me die? Would you at least feel sorry for me? Or would you laugh with Dad as you watched me dying? He bent and kissed her cheek.
Vader felt the turmoil of emotions from his son and watched as he stepped down from the platform and came over. Luke's head was down and Vader could sense that he had given up.
Vader was about to start to chain his son into the frame when the boy moved quickly and managed to plant a kiss on his father's shoulder. Vader pushed his son out of the way and saw tears on the boy's cheeks.
"I'm ready. Just do it and get it over with." Luke held out his right arm for his father to chain.
"I'll get it started, but it won't be over for a long time." Vader made sure that all the chains were lose and started to attach them to his son's limbs. Luke cried softly as he felt the chains go around his ankles, but he didn't bother to beg for mercy.
"What this machine will do is take the life force of a living creature and give it to a clone of a dead family member." Vader took one of the many needles that hung from the frame and pushed it under his skin of his son's wrist, "This will make sure that you don't pass out. The only way to extract the life force is through excruciating pain."
Luke nodded silently. He had counted on that much.
"These," Vader continued, pressing more needles under Luke's skin, "Will give your mother some of your living blood. Your heart will start hers and it will be as though you are one person with two hearts. These sensors are to monitor your shared heartbeat. There will be more happening, but I don't think that you are smart enough to understand what. Let's just say that your life force will be transferred to your mother. It should be enough to allow her to come back from the Force and to send you there in her place."
Luke whimpered suddenly and he fell to his knees. Vader ignored his son's pain and terror and started to tighten the chains so that Luke was lifted off the ground by one arm and hung there as Vader tightened the other chains.
Luke hung on the rack and watched sadly as his father turned the machine on. Goodbye, Father. I love you, he thought, before the machine started its grisly work.
Vader watched his son's pain without feeling. He had thought that there would be a sense of accomplishment watching the last Jedi die in agony, but he felt hollow.
It might have been because Luke hadn't been a full-fledged Jedi. Perhaps it was because Luke had given up. Perhaps it's because you're watching your only child die. Vader quickly banished the thought and returned his attention to the boy on the torture rack.
The boy who was his only son, the boy who loved him so much, the boy who was shrinking? Vader stared as his boy got smaller and his features became more rounded. It was like watching the boy lose his years.
Padmé's spirit was called from watching over her daughter, as she had watched her whole family since she had died, by her son's pain. She circled the room once, taking survey of the horrible scene, and joined with the clone body.
Suddenly Vader saw movement out of the corner of his eye. He turned and saw Padmé stirring. As he watched her deer eyes opened and she saw their terrified, screaming son, who now appeared to be about five.
Much to Vader's horror she stood and launched herself into the air at her son, tearing out all the needles and sensors. She caught Luke's tiny body in her arms and tore him from the torture rack, his smaller wrists and ankles sliding out of the cuffs with only a few scrapes to show for it. The moment the adrenaline IV tore out of his arm Luke fainted.
Padmé landed on the floor behind the rack and curled into a ball around her son in an effort to protect him from further harm. She saw her husband dashing over and kneeling next to her and managed to speak before she too passed out. "Keep our son alive. If he is dead when I come to, you will lose me too."
Vader started to say that Luke was really no great loss, but Padmé was already unconscious.