A/N: I know. Why am I writing this when I'm suppose to be updating Parenthood, but the idea just sort of snuck up on me and my muse just had to be satiated. This is sort of a sequel of Parenthood but you don't have to read that to understand. All you have to know is that Isaac, who is Sheldon and Penny's son from Parenthood, is fifteen years old here. Cass is twelve, Penny is pregnant with a third child and Sheldon had won the Nobel prize some time prior this. I may update Parenthood this weekend. Haha. Enjoy and please leave a review if you can.

Chaos Theory

Clow-san

The answer is there and he can almost see it. Brushing one formula aside, he drags back two from the side. The pattern is forming. Just a few more tweaks, a zero here and there, there-

"You should put on your seat belt, young man."

Fifteen year old Isaac Cooper snaps out of his mind palace and looks beside him at the source of the voice. It is an elderly woman with silver hair in an elegant bun. She reminds him of his Gramie both in appearance and her voice. He does not recall her sitting beside him but then again he quickly started on his formulas the moment he sat on his chair.

"Sorry?" He asks. He is always a bit sluggish whenever he spends a long time inside his mind palace.

"Your seat belt. We are landing in a few minutes."

"Oh." He buckles up. "Thank you."

He turns and stares out of the window. It is night out and he can see the beginnings of the brilliant lights that is the Los Angeles skyline. He pushes back the sleeve of his black sweater and looks at his wrist watch. 3:20 am it reads. December 21. He chuckles slightly. It is still set on time back in Cambridge. Mentally, he counts and sets it accordingly. Here at home, it is 7 in the evening. December 20. The plane sinks in the sky.

"Home for the holidays?" The old woman asks as the plane hits the pavement. The plane jumps and skids a little.

"Yes."

"That's nice." Her warm brown eyes trails down to the heavy navy wool scarf that is wrapped around Isaac's neck. "I hope you're planning on taking off that scarf. It's not as cold here as in London."

He opens his mouth to reply but the pilot's cool voice announcing their arrival cuts him off. As soon as the plane halts, Isaac stands up. He helps the old woman rescue her things from the overhead bin and helps her with her coat.

"Why thank you young man." She croons in delight. "I see your mother raised you right."

His ears turns red from the praise. "It's nothing, ma'am."

She smiles. "Happy holidays."

"To you too."

Los Angeles International Airport is jam packed with people. Isaac carefully maneuvers his way out of the baggage area with his large duffel bag slung across his body and moves towards arrival. It takes him about two minutes before he sees his targets. They are in a premium spot. Close enough from the gate to be spotted easily but far enough not to be in the middle of the throngs of people. He walks to them in a quick pace. He can see his sister in a comfortable green cardigan and jeans with her head bowed down an electronic tablet, no doubt working on her calculations. About three feet away, she looks up. Her heterochromic blue green eyes locks with his green ones.

Despite his joy in seeing her again in person, he knows better than to hug her. Instead he lifts his hand in greeting. "Cassie."

The twelve year old inclines her head. Her golden curls, in a single braid, shifting to the side. "Isaac."

"Cassie!" Another voice joins, in mock reprimand. "Is that how you greet your brother who's been gone for four months?"

He takes his gaze off her sister and smiles at the figure behind her. "Mom."

"Go on greet your brother properly." Penny Cooper says.

Isaac holds back a laugh. Only their mother can order Cassie around and get away with it. But then again she has been bossing their father for a long time. His sister sighs and hands her tablet to their mother. At an even six feet, Isaac towers over the women in his family. The top of Cassie's head barely reached his chest. She wraps her arms around his waist and though she is reluctant at the start, she tightens her hold of him.

"Welcome back, brother."

He pats her head. "Nice to be back, kiddo."

She lets him go and he turns to their mother. She looks so different from the last time he saw her. Her hair is styled differently, making her appear about five years younger and she must be using some sort of an anti-aging cream as well because her face seems younger too. But mostly the difference is her bulging and very pregnant abdomen. The last time she was in her third month and was hardly showing but now at almost seven months it is undeniable. Suddenly, he remembers how delicate his mother's condition is.

"Mom!" He exclaims. "Why are you here? You should be resting!"

"And he finally catches up." Cassie comments, dryly. "Been in your mind palace again?"

"Oh shush." Penny says, "I have enough of that from your father. Now hug me properly before I go Junior Rodeo on you."

"How did you persuade Dad to let you go here?" He grumbles against her shoulder, embracing her tightly but gently.

She smiles. "I still have a few tricks up my sleeves. Welcome home cupcake."

The drive home is full of catching up. It is as if Isaac does not talk to his family on Skype in a regular basis. Penny asks about Cambridge and his classmates. Cassie asks about the status of his dissertation. He asks about her college thesis. Though his field is Mathematics and hers is Physics, they understand each other very well. After all, Math is the universal language of Science and physicists have a working knowledge of the universe.

He learns that his mother has tricked his father into thinking that he is coming home tomorrow night. How she did that he cannot figure out. He finds out that his father is working late at Caltech putting finishing touches on his research about monopoles that may give him his second Nobel prize and will revolutionize the way people see that subject. He picks out how his mother's voice tightens when she shared this information. She is withholding something, he is sure. He catches Cassie's eyes from the back seat. Not now. They say.

Not long after, they are turning into a very familiar drive way and soon enough Isaac is afforded view of his childhood home.

It is good to be back.

The house looks pretty much the same. Though the office den is transformed into a nursery. Isaac remembers the long discussion he had with his parents, four months ago, when he was about to leave for England. He had told them to just take his room and that he will stay in the guest house when he goes home for the holidays and school breaks. Both his parents are oppose to the idea and says that as it does not matter if he is only home a couple of months, his room will always be his room. Now, however, as he surveys his room (his window seat at one side, his white board that dominates the right wall, his bed which has been changed three times in the last five years because of his growth spurt), he must admit that he never saw a more welcoming site. He makes his way to his white board and takes a hold of the dry ease maker in the scooped out section. He smiles when he realizes that the maker is brand new, courtesy of his mother no doubt in anticipation of his return. He puts his duffel bag down by his window seat before he takes off his black tweed coat and unwinds his wool scarf. He topples, face down, on his bed and savors the smell of the freshly laundered sheets. He does not know how his father does it, Isaac uses the same brand of detergent and fabric softener but his sheets back at his dorm room never smelled quite like this.

He is about to drift off to sleep, the last thirteen hours finally catching up on him, when he feel his phone vibrate. A text from his sister.

Rooftop observatory in five.

Ah, so she will finally tell him what is bothering their mother. Isaac quickly gets up and exits his room. He waves at his mother as he walks by her at the kitchen. He offers to help but she declines, stating that she is pregnant, not an invalid. He smiles and continues on, walking across the backyard to the spiral staircase just beside the guest house.

Isaac has many great memories of the rooftop observatory. Most of them with his family and his 'uncles'. They had spend many a nights here under the canopy of the stars. The position of the rooftop is optimal for observing one meteorological phenomenon after another using their high powered telescopes, and his mother said that this is one of the reasons why his father bought the property in the first place.

Cassie is sitting on one of the lounge chairs, when Isaac arrives.

"Hey sis." He greets. "So are you gonna tell me what's bothering Mom?"

She looks at him with a more sober expression than her usual.

"Tell me," she starts, "what do you think is the probability of Father ever having an affair?"