A/N: I'm taking certain liberties with the relationship between Lily and Petunia which I'm sure had deteriorated very much by the summer of Lily's sixth year but I do hope you enjoy anyways.
Petunia and Vernon Dursley were watching tv, their son Dudley beside them. Petunia wasn't paying attention, she was making a grocery list in her head: milk, bread…
"Look at him, you can tell by the look of him he's no good." Vernon said, bringing his wife back to reality.
Petunia looked at the tv, her heart sinking. On the screen was the face of a man she hadn't seen in years. He was changed, not the young man she had met all those years ago.
"Sirius Black is very dangerous man. If you see him do not attempt to stop him, call the authorities immediately." The woman on the tv was saying.
It was as if all the air had left Petunia's lungs. She stood up suddenly causing her husband and son to look at her. "Going for a drive." She managed to choke out as she grabbed her keys and headed for the door.
Petunia drove for a while before reaching a fairly deserted stretch of highway, pulling off to the side she turned off her car she reached for the pack of cigarettes she had hidden and lit one up, finally allowing her mind to wander to a night she had done her best not to think about for years.
"Lily they wouldn't want me there." Petunia said looking at her sister in the mirror.
"Of course they do Tuney." Lily said braiding her sister's hair. "In fact James asked me if you'd want to come. He wants to get to know you."
"I don't know Lily."
"Please. Pleaseeee."
Petunia sighed. "Alright fine. But you promise to bring me home if I'm uncomfortable."
Lily hugged her sister. "Of course Tuney." She tied her sister's hair off with a ribbon. "Alright ready?"
"How are we getting there?" Petunia asked standing up and putting on extra mascara.
"Disapperate." Lily said then noticing the odd look on her sister's face added, "It's magic. You just kind of disappear and go where you want."
"I thought you couldn't use magic outside of school."
"I can now. I'm seventeen. That's why we're celebrating. It's the first summer we're all allowed to use magic." Lily beamed. "You're going to have a blast."
"Okay. Do I look okay?" Petunia asked.
"Beautiful. Ready?"
"As ready as I'll ever be." Petunia said.
"Okay hold on really tight to my arm Tuney and don't let go. It's going to feel weird."
They appeared outside of the small cottage James and Sirius were renting. Petunia's face was white and her eyes were wide. Lily couldn't help but laugh at her sister.
"Looks like they're in the back." Lily said walking arm in arm with her sister to the back yard where there were several people already there, illuminated by the fire in the middle.
"Who's Lily's friend?" Sirius asked looking at the gate where Lily had just walked through.
James turned his head smiling at his girlfriend. "That's her sister, Petunia."
Sirius smirked running a hand through his hair.
"Sirius, be careful, Lily will kill you if you do something to her sister."
"Wouldn't dream of it." Sirius said still smirking.
"Who's that boy with James?" Petunia asked her sister. "He's staring right at me."
"That's Sirius Black. And he's staring because as I told you, you look stunning." Lily smiled at her sister, squeezing her arm before running off to jump in James's arm kissing him as he spun her around.
Sirius grabbed a butterbeer and headed over to Petunia. "Petunia is it?" Sirius asked.
"Yeah." Petunia said taking in the boy standing in front of her. He was handsome, and had a certain charm to him.
"I'm Sirius. Sirius Black. I thought you might want something to drink." He said holding out the butterbeer to Petunia.
"What is it?" Petunia asked taking the yellow drink from Sirius.
"It's butterbeer, and it's fabulous. Went and bought some from Hogsmead before we left school" Sirius said summoning a cup of firewhiskey to him. He grinned at the look of shock on her face at seeing someone use magic. Sirius held the drink up,"To the beautiful Evans sisters."
Rolling her eyes Petunia toasted with Sirius. He was right the butterbeer was delicious.
A blond boy walked over to Sirius and clapped him on the back. "Who's this Padfoot?"
Sirius turned to the boy grinning and pulled him into a hug. "Glad you made it Remus. Especially since we had to reschedule the whole thing for you." Sirius motioned towards Petunia. "This is Petunia. Lily's sister."
The boy, Remus smiled at her. "It's really great to meet you." He put out his hand. "You have her smile."
Lily snuck up behind him. "I hope you mean that in a good way Moony."
Remus turned to the redhead smiling. "Of course I do Evans." He pulled her into a hug and looked around. "Where's Peter?"
"Late, as always." James said checking his watch.
Lily grabbed her sisters hand and pulled her away. "Be back in a second boys." She pulled her away making her way to the table and pouring herself a drink.
"They're nice." Petunia said to her sister.
"I told you!" Lily said tapping her wand on her glass, the liquid inside turning a light pink color; Lily nodded looking satisfied. Lily paused for a second. "Tuney, you be careful around Sirius."
"What do you mean?" Petunia asked.
"Nothing bad, I don't mean it like that. I love Sirius he's James' best mate but he's been known to…he's a charmer."
"I've been around boys before Lils." Petunia said smiling at her sister. "I don't think magic really changes their behavior that much."
Lily laughed. "I miss you Tuney."
"I miss you too." Petunia said, glancing back at Sirius. "He is cute though."
Lily shook her head. "You're just like all the other girls in our grade."
Sirius glanced over and saw the two girls laughing. Pointing his wand at the turn table he had stolen from his brother's room he turned it on, he smiled at James who had charmed the music to be louder than it normally would.
It was beginning to get dark and more people had turned up since Lily and Petunia had arrived. Lupin was off talking to some girl who Sirius recognized as a Hufflepuff and Peter was walking around looking uncomfortable.
Sirius caught Petunia's eye and winked at her. He drank the last of his firewhiskey and walked over to the girls. "Care to dance." He asked Petunia offering his arm.
Petunia nodded, a smile forming on her lips. She took Sirius's hand. It was rough. Sirius pulled her out to the dance floor spinning her around. Petunia didn't recognize the music playing and when she realized it was probably wizarding music she felt a stab of sadness in her heart that she would never be like her sister.
"I like this music." She told Sirius as he dipped her backwards.
Sirius smiled at her pulling her close. "You know it's a shame you aren't a witch."
Petunia's eyes got wide and her body stiffened she was clearly offended.
"I don't mean it like that." Sirius said pulling her closer to him as she tried to pull away. "I meant, I think I'd rather like for you to have gone to our school."
Petunia didn't seem convinced and still looked a little put out.
"Listen, tonight it doesn't matter what you are. You're here and we're going to have fun. " Sirius smiled, pulling out his wand he conjured a Petunia and placed it behind her ear.
"You're something else Sirius Black." Petunia said laughing as he spun her around.