(Note: If you haven't read part one, scroll down to the artist comments for links.)

'Good night, birthday girl!" Nicole's mom said from the doorway. "I can't believe it, my little girl, eighteen years old…"
"Thanks mom. Good night!" Nicole called from the bed where she was lying down.
'Goodnight, Mrs. Green!" Rachel added. She was lying on top of her sleeping bag, spread out on top of a cot next to her friend's bed.
Both girls had changed into their clothes for bed; Rachel was her pajamas. Nicole had on an old t-shirt of her father's she almost disappeared in.
"Finally…" Nicole thought to herself, somewhat unfairly, as her mom got the hint and left, closing the door behind her. A shy girl, Nicole had never been comfortable as the center of attention, so it wasn't surprising she found being the "birthday girl" more trying then fun.
At least she'd managed to convince her mother on a modest party. Her family had gone out to a movie, along with her best friend Rachel, and Rachel's two sisters, Laura and Sarah.
They'd returned home and the girls had run around the backyard, generally having a good time, while Nicole's dad torched some steaks on the grill, followed by cake and presents; Nicole had a new sketchpad and pencils, courtesy of Rachel, a couple books from her parents, a gift card from her uncle and cousin, and a particularly bad sweater from her grandmother.
Sarah and Laura had gone home after that, while Rachel was to stay the night with Nicole. They'd done all the usual sleep-over things, make popcorn, watch bad late night horror movies and play video games until their eyes hurt, had an impromptu pillow fight which ended with Nicole roped up like a hog for some serious tickle torture, and generally had fun, and above all made a mess.
Finally, an hour or two past midnight, Nicole's mom had gotten up and finally told the two that, birthday girl or not, it was time for Nicole and her guest to go to bed.      

"Now that your mom's gone, I can give you your other present…" Rachel said, getting up from the cot. She walked over to her backpack and pulled out a package wrapped in brown butcher paper.
"What present?" Nicole asked.
"What, just tell you? And ruin the surprise?" Rachel said, beginning to unwrap the package. "Sarah got it, don't ask me where, and asked me to give it to you for her; thought we could use it in our games. She said now I won't have to borrow hers anymore…"
Nicole grinned. If Sarah had gotten it, it must have been some sort of bondage-device, which explained why she couldn't give it to Nicole in front of her parents. While Nicole and Rachel had to make do with whatever rope or tape they could scrounge up for their own "tie up games", Sarah and her boyfriend, Mason, both college students with jobs, could spend a little money on "toys" for their own games.
"Turn around and close your eyes." Rachel said, hiding the unwrapped present. Nicole glanced at the door. "Don't worry," Rachel said, knowing what her friend was thinking. "I'm sure your mom's gone to sleep. We won't be bothered."
Nicole shrugged. She grabbed a hair tie and pulled her brown hair back into a pony-tail, to keep it out of the way while they played. She turned and closed her eyes. Even though she was expecting something, it still took her by surprise when Rachel stuffed a rubber ball between her teeth.
"How's it feel?" Rachel asked, playfully, as she pulled the leather straps back behind Nicole's head and buckled it tight.
"Hmmmppphhh!" was all Nicole could say as reply. Her jaw was stretched as far as it could go, it seemed.  
"Good. Sarah was worried the ball gag might have been too small for you." Rachel said with a chuckle. "Now, as long as your gagged, I guess I might as well tie you up too. Where are your things?"
Nicole grunted into her gag, suggesting without words that it might have been better to ask her that before she'd been gagged and was able to tell Rachel. She gestured to the closet. After some searching, Rachel found a shoebox and pulled out a couple short lengths of rope.
Nicole turned and presented her hands for Rachel to tie them. As she worked the ropes, Rachel chatted amiably with her captive.
"By the way, speaking of my sister, it's about time we got back at her for kidnapping us." Rachel said.
Nicole groaned into her gag. She'd hoped Rachel had forgotten all of that. About two weeks ago, Rachel had "borrowed", some of Sarah's bondage things for one of their tie up games while she was visiting friends. Needless to say, when Sarah had returned, she hadn't been too thrilled, and the two teenagers had been taken captive.
Personally, Nicole, a true submissive, had found being kidnapped by Sarah as a "slave" to serve snacks at her friend's party more exciting than anything else, but things were different for Rachel. She was Sarah's sister, a humiliation like this demanded revenge, in true sibling fashion.
Rachel finished tying Nicole's hands and moved down to her feet, at the same time, explaining her plans.
"In two days, Sarah's got a date with Mason. She won't be back until late that night and she always ends up sleeping in late the next morning. We can prepare a little "surprise" for her…"
Nicole listened as Rachel outlined what she had planned in store for her sister, occasionally "mmmppphhh-ing" agreeably into her gag. Had she been able to talk, she could have added some suggestions. Still…this sounded like fun…

***

"Yeah, Catherine…" Sarah said into the cellphone. 'I'm sure of it. She's planning something…really, I'm surprised she's managed to hold off this long without trying something...she's probably going to get her friend to help her out…I just need a little help from you…we'll prepare our own little surprise for them…"