Sheldon sat in his spot; he felt something was wrong. Something had changed. Sheldon disliked change. Yes, everything changes over time, he knew that, but this was affecting him.

He looked around the apartment trying to pinpoint the thing which was troubling him.

Something was missing. He needed more data.

He despised obscurity.

Life required order and structure. Without it, only confusion and disorder remained. Sheldon began silently reviewing possible contributors to his unease.

He had not eaten yet, so it was not food related.

Amy's imminent move abroad had caused only a momentary change in his daily schedule.

No, this change was far bigger than just a friend moving abroad.

A sound from the kitchen area dragged him from his thoughts.

Leonard laughed at something Priya said; he had his arm around her shoulders.

Sheldon shook his head, and sighed. Oh how he wished they could return to the days when the only female problem they had lived across the hall.

He stood quickly, moving down the hall to his room.

Leonard watched his roommate move past him "You ok there, buddy?"

Sheldon stopped at the sound of Leonard's voice, glancing over his shoulder. He looked at Leonard. Buddy? He shook his head before turning and going over to his desk. Picking up his laptop, he walked back to his bedroom.

Some time ago, Sheldon had formulated an algorithm to better understand: 'friendship'. Even so he was still at a loss to understand Leonard's constant need for female approval. The algorithm contained all up to date data on his friends. He recently had reviewed Penny's file, due to her foolish night of coitus with Raj.

Sheldon frowned. This illogical move on Penny's part had led to her being banished from the apartment.

As he sat on his bed waiting for his computer to finish his friendship program, Sheldon knew what was missing.

Leonard and Priya were sitting on the couch as Sheldon walked from his bedroom and made his way to the hallway door.

"Hi! Sheldon" Leonard was a little confused by his roommate's behaviour. "Going out?"

Sheldon stopped at the front door and looked over his shoulder at Leonard. "Yes" and with that he was gone. Not far as it turned out. Just as Sheldon left his apartment, Penny walked up the stairs.

He could see by the dark rings under her eyes and the puffiness of her face, life was not going well for his friend.

"Hello Penny. How was your day?"

Sheldon could see she was holding herself in check, fighting so hard not to reply with some sarcastic remark.

"Not so well Sheldon, do you want something?"

By now she was at her door; she turned and found him standing next to her "Sheldon please what is it?"

"Penny, you're my friend. I'm lead to believe friends converse"

He took a step back waiting for her reply.

Penny leaned against the door frame. Sheldon could see she was fighting to stop herself crying. She sighed before turning to face him.

"Look I've been banished from your apartment, so how can you be my friend?"

She looked at him. The full realization finally hit him his friend, Penny, was the only thing missing from his life.

Standing up to his full height, hands behind his back he faced her. "Penny, you seem to be under the false assumption that I am no longer your friend" With his head only slightly to one side, he waited for Penny to answer.

"So you don't hate me?" her voice was barely a whisper.

"You have done nothing to invalidate our friendship agreement. You did, however, display a certain lapse in judgement. Raj was possibly not the best candidate for coitus".

Sheldon saw the shadow of a smile on her face.

"Penny as we seem to have forestalled any doubts you may have had regarding our friendship, may I invite you to dinner".

Penny was taken aback "You're asking me out to dinner?" Sheldon's eyebrows shot into his hairline. It seemed to take him a moment to speak.

"Lord, No! I'm asking you to join me in my apartment for takeout"

She smiled shaking her head. "Sorry. What was I thinking?"

Sheldon wondered what Leonard and Priya would make of his dinner guest. Looking down at her, he saw Penny's genuine smile finally return. Sheldon smiled back "I'll order extra dumplings".