I don't own! JK Rowling does!
The marauders were sitting in their compartment on their way to begin their 2nd year at Hogwarts school of Witchcraft and Wizardry. They were planning some kind of mischief or another when Sirius said he had to use the little boys room. He got a couple grunts so he turned to leave.
But outside the door he met the worst person he could meet on the train, all by himself. His cousin. Bellatrix Black.
She smiled a wide and gross smile, "Hello, little cousin."
Sirius pulled out all of his courage and looked her full in the face, "Hello, darling Bella."
He face contorted slightly, "Don't call me that." She spat. Sirius almost smiled at being able to get a reaction out of her but decided it was best for his life if he didn't.
"What do you want Bellatrix?" he asked. Her eyes glittered with malice, "Oh, I just wanted to visit you." Her gross and unhealthy looking smile was back. Sirius was about to reply when James came out of the compartment.
"Hey Sirius, you forgot your…" he stopped when he saw Sirius's cousin, the one who often gave Sirius nightmares. He narrowed his eyes are her and closed the compartment door, "What do you want Black?"
"James, get back in the compartment!" Sirius hissed at him. James ignored him and Sirius groaned internally. Bellatrix was not someone to mess with, she was dangerous.
"No, no, little bitty Potter can join in the fun," Bellatrix cooed. Sirius now knew was James was going to say. He doesn't have his wand! James started to raise his wand but Bellatrix was too fast.
"Expelliarmus!" she said and James's and Sirius's wands both flew to her. She smiled again and said, "Imperio!" on both of the boys. She forced them to crawl under their compartment window so the filth inside wouldn't see them. Both boys tried valiantly to throw the curse off, but it was in vain. Finally she let them walk and into an empty compartment a few down from theirs.
She drew the curtains and took the imperio off of the boys.
"What do you want?" James hissed again, while Sirius was planning a different approach.
"Bellatrix, it's me you want! Let James go!" he said pleadingly, and it took a lot to make Sirius Black plead.
"Stop being noble! I am NOT leaving without you!" James hissed at him.
"I'm disgusted to be related to you! Pleading, and for a blood-traitor no less!" she glared at him. The boys looked at each other and suddenly charged, trying to push past her at the same time. They had the element of surprise and almost got away but Bellatrix was 17 and the boys had just turned 12.
"Oh, no, no, no that won't do." She said. She put a body bind on Sirius and silenced James. Sirius looked fearfully at Bellatrix and she twirled her wand and James was yelling profanities at her at the top of his lungs but no one could hear him. Bellatrix smiled maliciously again and yelled the word Sirius had prayed she wouldn't.
"Crucio!" she yelled sweetly. James immediately stopped yelling silently and began to writhe on the floor screaming silently in pain. Sirius tried as hard as he could to move but he couldn't and all he could do was watch helplessly as his best friend was tortured by his insane cousin. Bellatrix quit about 5 minutes after James had passed out. She woke him up with a spell and body binded him like she had Sirius and put the silencing charm on Sirius after she took off his body bind.
"Your turn, Siri" she cooed. Now it was James's turn to watch silently as his best friend bended his body in weird angles on the floor trying escape the pain. Hot tears had been running down the faces of both boys since the first crucio had been uttered. Finally after Sirius had passed out she stopped and woke him up with the same spell she had James.
"How was that, baby cousin?" she asked sweetly. Before he could even open his mouth Bellatrix had shouted, "Petrific Totalus!" so his legs and arms snapped together and his jaw jammed shut. She kicked both boys onto the floor. She kicked them repeatedly and used spells to cut them and watched them bleed with fascination. James was the first to pass out from blood loss and Sirius knew that Bellatrix had gone worse on James on purpose. Her own payback since Sirius had pleaded. Sirius was on the verge of passing out and she punched him hard in the nose to a sickening crack.
He tried to stay awake but the last thing he heard was, "You just endangered these mudblood loving sickos even more by befriending them. I know Potter won't want to be your friend anymore after this and your family certainly won't want you back!" She laughed viciously and took off the two body binds and quickly left and shut the door and curtains behind herself. Sirius passed out with Bellatrix's words still running in his head.