It was a couple days before Halloween. Gon, Kurapika, Leorio, and Killua were at Gon's house on Whale Island, helping to set up for a Halloween party. Gon was helping Killua put up various spooky wall hangings and window clings, while Kurapika was busy picking out music for the party, and Leorio was getting himself tangled while trying to put the Jack-o-Lantern streamers up. Gon's aunt Mito was checking the RSVPs, which consisted of most of the Hunter applicants.

"Help, help!" Leorio called while trying to get himself untangled from the streamers. "Somebody help, help!" Gon, Killua, and Kurapika looked to see poor Leorio in his silly predicament, and laughed. "Hey, quit laughing and help me!"

"Sorry, Leorio," Gon said and, still chuckling, went over to his friend and helped him get untangled. "There."

"Thanks," Leorio said and got back to putting the streamers up.

"No problem," Gon said cheerfully, then went back to helping Killua with putting up the other decorations. "This is gonna be the best Halloween party ever!"

"I'm sure it will be," Kurapika replied. He, Gon, and Killua cringed as they heard a loud thud. They turned in the direction the sound was coming from and saw Leorio on his back, on the floor, the step ladder he was using tipped over. He had fallen over while finishing with the streamers.

"Ouch," Killua commented. He, Gon, and Kurapika went over to Leorio to see if he was okay.

"You okay, Leorio?" Kurapika asked as he and Gon helped the guy up.

"Yeah, I think I'll be okay," Leorio said as Mito came running to see what happened.

"What's going on?" Mito asked. "Is everything okay?"

"Everything's fine, Aunt Mito," said Gon with a smile. "Leorio just fell over, but he's okay."

"Oh, okay," said Mito. "As long as everything's okay here." She got her purse and went to the front door. "Will you guys be alright while I'm out? I need to pick up the food and drinks for the party. I'll be right back."

"Sure, we'll be fine!" Gon said and grinned. "See ya later! Hey, Aunt Mito, how many people RSVP'd so far?"

"Just about everybody you invited," Mito replied.

"Awesome!" Gon exclaimed as his aunt left for the store to pick up the party refreshments. He and his friends then went back to setting up the party decorations. After Mito came back with the snacks and drinks, they helped her put them away for later use.

Two days later

Halloween finally arrived. Gon, dressed as Naruto Uzumaki, happily greeted each of the guests as they filed into his house, then rejoined Killua—dressed as Sasuke Uchiha—Killua's younger sibling and +1, Alluka, who was dressed as Sakura Haruno, and Canary, a butler of the Zoldyck family, who was dressed as Tweety Bird. Leorio—dressed as Harry Potter—and Kurapika—dressed as Batman—also joined the quartet in their revelry.

A few moments later, Gon screamed after hearing someone behind him say, "Why so serious, Gon?" He whirled around and punched the voice's owner in the face. It was only a couple seconds later that he realized he had punched Hisoka, who had come to the party dressed as the Joker from The Dark Knight.

"Now, why did you go and do that?" Hisoka asked calmly while wiping his bleeding nose.

"Oh, it's you, Hisoka," Gon shakily said. Then his face lit up after remembering something. "Hey, I finally punched you in the face!" He took out a badge with the number 44 on it and threw it to Hisoka. "I can finally give this back to you, and use my Hunter License!" Hisoka picked his badge up and got up off the floor.

"Wow, you finally punched Hisoka," Killua said.

"Yeah!" a happy Gon replied. Just then, he, his friends, and the other guests heard Mito talking to someone at the door. Gon, Killua, Alluka, and Canary went to see who it was. Killua and Alluka groaned upon seeing who it was: Their older brother, Illumi, who was dressed as Edward Cullen from the Twilight saga.

"Excuse me," Mito said and took out a piece of paper. "Are you on the guest list?"

"Of course I am," Illumi replied calmly. "I'm Illumi Zoldyck."

"Illumi Zoldyck…" Mito muttered, scanning the list. "I only see two Zoldycks on here: Killua and Alluka." She lowered the list and looked directly at Illumi. "Sorry, but you're going to have to leave."

"I will not leave," Illumi said, his blank eyes practically staring into Mito's soul. "I was sent here to watch over Kill."

"Get out of here, Illumi, you jerk!" Gon exclaimed. "I didn't invite you! And Killua and Alluka don't seem to want you here! Believe it!"

"I'm not leaving," Illumi replied and just sat on the ground outside.

"Suit yourself," Canary said. She and the others went back inside.

"Geez, what a jerk," Killua commented. "And showing up here as Edward Cullen, of all people?"

"I know," said Alluka. "Talk about bad taste."

"Okay," Mito said with a huge sigh. "Now that that guy's out of our hair, let's just get back to having fun, okay?"

"Heck yeah!" Gon, Canary, and the Zoldyck siblings said, then went back to their friends.

Later on, the fun was interrupted once again by Kurapika screaming at the top of his lungs, and chasing what looked to be a giant spider around the house with a baseball bat.

"Quit running, so I can hit you, you eight-legged freak!" Kurapika shouted as Leorio, Hisoka, and some of the other guests ran after him, trying to stop him.

"I'll stop running if you quit chasing me with that bat!" the spider yelled back at Kurapika. The spider stopped running when Ponzu and Pokkle tackled Kurapika, causing the Batman cosplayer to drop his weapon. The spider panted, then turned around, revealing itself to be Tonpa in a costume.

"Get the hell off me!" Kurapika screamed.

"It's okay, Kurapika," Gon assured his friend. "It's just Tonpa."

"What are you doing here?" Leorio asked in an unenthusiastic manner.

"He's my +1," Hisoka explained.

"Oh. Great," Leorio said sarcastically. After helping Kurapika calm down, he said, "Well, just make sure he doesn't try to spike the punch."

"Why would I do that?!" an offended Tonpa asked.

"Because you tried that during the last Hunter Exam, you Nimrod!" Leorio said back.

"So?" Tonpa asked.

"So, I don't trust you not to spike the punch," said Leorio.

"Whatever," said Tonpa.

"Hey, can I ask you something?" Leorio asked.

"What?" said Tonpa.

"Did you dress up as a spider just to get a reaction out of Kurapika?" asked Leorio. "Because if you did, that's pretty low, even for someone like you."

"Maybe," Tonpa replied in a singsong voice, then went to do his own thing.

"What a jerk," Leorio mumbled and went back to join his friends.

Later on, Mito announced the costume contest. People lined up to have their costumes judged. Gon, Killua, and Alluka won First Prize for Best Group Costume. Tonpa got Last Place for Best Solo Costume, while Kurapika won First Place for that category. Hisoka won Second Place for Best Solo Costume, while Leorio got Third.

After the party ended, everyone spent the night at Gon's house. Illumi still sat outside, occasionally spying on everyone through the window. Killua woke up once during the night, only to see Illumi looking right into the window. He opened the window and punched Illumi's lights out, then closed the window and went back to bed. Illumi stayed unconscious the rest of the night.