Disclaimer: I do not own Numb3rs or the characters. No copyright infringement is intended. The math in this story is from Wikipedia.

A/N: Set in Season 2. Thank you, everyone, for the reviews! To show my appreciation, I'm posting two chapters at once. And special thanks to my beta, seether79!

Chapter 2

After stepping off the elevator, Charlie and Amita followed a trail of water to find Colby standing in the middle of a row of cubicles threatening, "And believe me, you're gonna pay!"

David was clearly struggling not to laugh as he said, "I don't know what you're talking about. Why? Did something happen?" Abandoning any attempt to maintain a straight face, he doubled over laughing and grabbed a nearby desk for support.

"Laugh it up," Colby grumbled as he wrung water out of the ends of his shirt. "You're next!"

Charlie covered his mouth, but couldn't hold back his own laughter.

Colby spun around to face him. "And what's your story, huh? Were you supposed to make sure I was in position?"

Charlie's eyes went wide, and he held up his hands. "Hey, don't look at me! This wasn't my idea."

Before he could say more, Don's voice rang out from the back of the room. "Alright, people. Whatever you're discussing out here, let's try to keep it down to a low roar, huh? Some of us would like to get our work done and get out of here while there's still a little weekend left, you know?"

When he neared Colby, Don stopped in his tracks. Looking him up and down, Don screwed up his face in a puzzled expression. "What happened to you?"

"I'll tell you what happened to me! I went out front looking for Charlie like you asked me to and these clowns thought it'd be funny to drop water balloons on me."

"Oh, yeah?" Don asked in a confused tone as he resumed his path down the hallway. "Why's that?"

Colby fell into step beside him and continued complaining. "Because they're immature idiots, that's why!"

As soon as they rounded the corner, the rest of the agents burst out laughing. Only a few people were in the office and clearly things were a little loose today.

Charlie chuckled and shook his head in admiration. If he hadn't known for a fact that Don was involved, he might have fallen for his act too. Turning to Amita, he commented, "You have to admit, he's good."

"Hmm… 'Good' might not be the word I would choose," she replied with a smirk. "You do realize he set Colby up don't you?"

Still smiling, Charlie leaned against a desk and nodded. He'd caught Colby's comment that Don had been the one to send him out front.

Amita raised an eyebrow. "And you don't think he asked you here today for the same reason?"

Charlie immediately shook his head. "No, Don wouldn't…" His words trailed off as he considered the possibility. He reviewed the phone call in his mind.

"I mean, if you're in the middle of something, it can wait. But if you could come by this afternoon, I'd really appreciate it, buddy."

Charlie's eyes narrowed as he turned to look in the direction Don had just headed. "He set me up!" Looking back at Amita, he noticed she wore a self-satisfied expression.

"Why are you smiling?" he asked, perplexed. "He ruined your Sunday too, you know."

Amita shrugged. "I guess I just like figuring something out before you. Doesn't happen that often." Tilting her head slightly, she added with a shy smile, "Besides, I wouldn't say the day was ruined."

"Yeah, well…" Charlie trailed off and ran a hand through his hair in frustration, uncertain what he wanted to say. He felt like there was something in Amita's comment he ought to pursue, but anger at his brother was making it hard to think. "I'll be right back," he assured her quickly before storming off in search of Don.

Charlie found him a minute later in the office's small kitchen. But he drew up short at the wide grin on Colby's face. Colby was leaning against the counter, nodding and listening intently. Don stood beside him, one arm slung over Colby's shoulders and the other hand gesturing furiously as he whispered in Colby's ear.

Charlie sighed, understanding immediately what had happened. Don had invited Colby into the game. And Colby, standing there in wet clothing that clung to him, was falling for every word. Charlie couldn't blame him. It'd been that way since Don was a kid. He had a talent for making it seem like joining up with him was the best idea in the world. He used it with witnesses, with suspects he pressed for confessions, and apparently with the victims of childish pranks.

Charlie crossed his arms and waited. He was determined not to fall for it this time. There was nothing Don could say to make up for the fact that calling him down to the office on a Sunday just to become a target had been a nasty trick.

The two agents were so focused on their discussion that Charlie didn't think they'd noticed his arrival. But apparently he was wrong. As Don dropped his arm from Colby's shoulder and reached for his coffee cup, he said without bothering to look up, "And take Charlie with you."

Colby looked insulted. "I think I know how to drop a water balloon, thanks."

Don slowly stirred the contents of a Splenda packet into his coffee. "Yeah? What's velocity?"

"You know…um, how fast something travels," Colby said.

Don locked eyes with Charlie and gave him a slow, knowing smile. And despite his best intentions, Charlie felt himself smiling back.

Ignoring their silent exchange, Colby stalked off. The brothers' eye contact was broken as Colby passed between them and Charlie shook his head as if awakening from a trance. "Forget it," he grumbled.

Don shrugged casually. "Fine."

Charlie gestured irritably in the direction Colby had headed. "He… he knows what velocity is. He's ex-military. Of course, he knows. He just… doesn't know he knows."

Don nodded calmly. "Uh-huh. Okay, Charlie. Whatever you say."