Summary: Andromeda is the proof.
Sirius Black was a horrible little boy, and Narcissa hoped he fell in a pit of spiders and died.
"Bell-lla," she whined. "My arm's getting sore. I can't hold it up anymore." She let it drop a little, the wand faltering in her hand. "Your wand is too heavy."
Bella had climbed up to a precarious perch near the dark ceiling, trying to work out how to open the stupid invisible trapdoor to this stupid oubliette in Grimmauld Place that stupid Sirius had told them was a shortcut to the back garden. She jumped down, now, and Cissy quickly raised the lit wand to the right height again, casting the blue glow into every corner of the weird tiny space.
Bellatrix took three steps towards her. "In another year you'll have to carry a wand all the time," Bella said, leaning in close. The wandlight cast blue shadows on her face, making it ghoulish. "They thrash you, at Hogwarts, if you let your wand arm fall."
Narcissa backed up a little, her shoulders crowding against the wall, and Bella followed. "And do you know what they do if you drop your wand during a spell?" Narcissa leaned back further, and Bella widened her eyes. "They hang you by your thumbs until your thumbs go black and fall off, and then they drag you into the Great Hall to be an example to everyone."
Cissy breathed quickly for a moment. "I don't believe you," she said. "You're lying. You always lie."
Bella grabbed her wand, trapping Narcissa's hand around it. "They do it if you're my sister," she said.
... so Bella had moved on to the definition of They where she meant Bellatrix Black. Cissy screwed up her face. "They wouldn't let you do that," she said, mostly sure. She was still breathing too fast, though.
There was a scrape and a crash from above, and Bella snatched her wand back and aimed it at the ceiling. The trapdoor reappeared and then flipped open, and dusty daylight filtered down, overwhelming the sickly wandlight.
"Andromeda!" Cissy cried, pushing up beside Bella.
Andromeda leaned in, making a face at the dust that rose. She was holding Sirius by one arm while he strained to get away. His small body was practically levitating sideways with the effort.
"You little beast," Bella said, her eyes snapping onto Sirius. "I'm going to gut you and tell the house elves to turn you into Black pudding and feed it to the fairies and first I'm going to cast a spell to make sure you stay alive the whole time."
"Then he did trick you?" Andromeda asked. "I wasn't sure whether he was devious enough. Reggie told me sometimes people just get lost and fall in." She wrinkled her nose, leaning over to peer down into the corners of the little space Narcissa and Bellatrix had been trapped in. "These old pureblood houses have terrible designs."
Bella was still watching Sirius. His eyes had turned towards her, as though his gaze had been dragged against his will, and he looked a little grey. "Let us up," Bella said very deliberately to Andromeda, not taking her eyes off her cousin.
Andromeda sighed and let go of Sirius, giving his shoulder a push. "Shove off, then," she said. "You're going to need a head start, I expect."
Sirius took off like a shot.
"We're here for another three days, you know, you suicidal little brat!" Andromeda called after him.
Finally she let down the silvery net rope that had been tied up on the upper side of the trapdoor. She caught Bellatrix's arm as her sister reached the top, stopping her for a moment.
"Bella. Don't do anything too awful to him." She sounded anxious, and as though she didn't want to sound anxious. "Remember he's only five."
Bella shook Andromeda off and got to her feet. "Don't," she said dangerously, "tell me what to do." She stalked off, out of Narcissa's line of sight.
Andromeda sighed and held out her hand. "Reggie's sitting down to tea on his own," she told Narcissa. "He'll probably give all our cakes to Kreacher if we're not there."
Narcissa let Andromeda pull her up. She looked down at herself as soon as she was properly in the light again, and made a distressed sound. Her nice blue robes were filthy.
"You might have cast a Sonorous and shouted for help, you know," Andromeda said, aggressively sensible as usual. "You never think of the obvious thing to do."
Narcissa brushed at the dirt on her robes, tears pricking the corners of her eyes. They were nearly her favourite robes, and everything was suddenly too much. "I don't know how!" she protested. "And Bella wanted to work out the mechanism and she wouldn't let me help except to hold the wandlight, and nobody knew where we were, and my arms got so tired so she told me she was going to hang me up by my thumbs and they don't do that, do they, at Hogwarts?"
Andromeda only rolled her eyes. "Don't be a baby," she said. "You could have got out of there if you'd really tried. There's a way out of anywhere if you look hard enough." She pushed Narcissa in front of her to get her walking, and they started down towards the nursery where the tea things were laid out.
From somewhere in the depths of the house, there was a crash and the sound of running feet.
Narcissa took comfort in the fact that apparently neither Sirius nor Bella was coming to tea. At least there'd be more cakes. As long as Regulus hadn't really given them all away to his favourite house elf.
She quickened her steps.
Andromeda hadn't put the ring on. She was sitting with it in her hands, tilting her palms to make it roll over and back, glittering in the light coming through the bedroom window. Her expression was bleak but weirdly detached, like somebody considering a scorpion poised to sting her, and wondering whether the experience would be an interesting one.
Narcissa's patience gave out. "Is it so bad?" she burst out. "Don't you want to even a little?"
Andromeda looked up, that queer trapped expression still in her eyes. "I would rather be locked in Azkaban for the rest of my life," Narcissa's sensible, literal-minded sister said.
Narcissa curled her knees up on her chair, hugging them. "It's only marriage," she mumbled.
Nobody would expect Cissy to marry for years yet, but she'd already decided who it would be. She'd started dropping Lucius Malfoy's name in her mother's presence at careful intervals. From the amused and rather pleased glances Druella Black had taken to giving her, Narcissa read her answer as: Owl received and understood, my darling daughter, and I'll see what I can do.
"Everybody gets married," Narcissa said. "Is it so bad?"
Andromeda gave her a look from somewhere on the scathing far shores of misery. Narcissa felt young and stupid and like she'd never had less idea what to say.
The door banged back, and Bellatrix swept inside. Her eyes lit on the ring. "So it's true," she breathed. "They got you."
Andromeda's eyes narrowed. "Thank you for your support, dear sister," she said. "Yes, I have an engagement ring. Isn't it pretty? Is it prettier than yours?" She held it up, dangling it from her fingers like a slug.
Bella pushed herself up onto Andromeda's desk, crossing her legs into Andromeda's space so that her sister was forced to lean back in her chair. Bella leaned forward, her eyes wide. "You're not saying this wasn't what you wanted?" she said. She stroked back a curl from Andromeda's cheek. "Darling sister, I thought it must be. Why else would you have been carrying on with –"
"Shut up," Andromeda said dangerously.
Bellatrix looked delighted. "You know that's why they're pushing this, though," she purred. "They would have let you have years, yet, if it wasn't for that boy ..."
Andromeda stood in a rush, making Bella laugh and nearly topple from her seat. "I mean it, you can shut up about that. There's nothing to talk about."
Narcissa glanced from one to the other of them. She twisted her fingers. "But Drom," she said finally, "Is it because of that boy? That you mind, I mean?"
Andromeda whirled and threw the ring at her. "There is no boy!" she cried. "You have no idea what you're talking about! Both of you, just ... just get lost! Get out of here and leave me alone!"
Narcissa stared at her for a moment, shocked. The ring had hurt, striking her cheek.
"Did we strike a ne-erve?" Bella sing-songed.
"GET! LOST!" Andromeda bellowed, throwing a wall of wandless magic in their direction, and Narcissa fled. A moment later Bella followed her out, still laughing, pursued by tiny green dragons.
Narcissa was a little relieved to see them. The wandless magic had been unnerving, but Andromeda had always been good at the dragon spell.
Bellatrix leaned in towards Narcissa, kissing her cheek through her hair. "She's going to be so much fun the next few months," she sang.
"I suppose," Narcissa said. She looked back over her shoulder at the closed bedroom door as Bella danced on down the hallway.
Later she wondered whether it would have made a difference, if they'd refused to leave her room that day. Would Andromeda still have found the opportunity to elope, if Bella and Cissy hadn't got lost when she told them to?
It wasn't Lucius who brought Narcissa to the Dark Lord. Lucius had never been able to make Narcissa do anything she didn't want to do. Bellatrix, though, could make her do things by convincing her that she secretly wanted to. Bella wouldn't be half as dangerous as she was, if she were only a little less charismatic.
Now Narcissa stared up into Lord Voldemort's dark eyes, more charismatic and crazier by far than Bella's, and thought, panicked, This was the wrong decision.
"And will you serve me, Narcissa Malfoy?" the Dark Lord asked, his voice a silky rasp.
"I would be honoured, my lord," Narcissa said, sweeping her curtsey as low as she could make it. She could see the enormous snake out of the corner of her eye, still feasting on the sacrifice its master had given it. Terror slithered sickly in her stomach.
When she was finally allowed to step back, out of the burning brightness of the centre of the circle, melting as much as she could into the other black cloaks and hoods, she instinctively sought out Bellatrix's face across the circle. Bella's hood was pushed back, her whole body yearning towards Lord Voldemort's pacing figure as he addressed them. There was a feverish light on her face. She wasn't, Narcissa realised, holding back with a single particle of her being.
Narcissa would have liked to go to her, try to work out a strategy for retreat, but she could see immediately that it would be no good. Bellatrix hadn't even noticed how lost they both were right now.
She ducked her head, pushing her thoughts and emotions as far down as she could. Lucius, beside her, took her hand, and she let him, absently patting his fingers with her other hand.
No one was ever entirely lost, she thought. Hadn't Andromeda said that once? There's a way out of anywhere if you look hard enough. Narcissa didn't say Andromeda's name anymore, but she remembered that, and held onto it, and her breathing calmed a little.
Those words, after all, had been spoken by the sister who'd proven them true.
For the prompt: Three times Narcissa and Bellatrix got lost together. (Interpreted fairly broadly.)