"Mycroft!" Sherlock shouted down the long hallway, his tiny voice echoing off the walls. "Where are you?"

Mycroft Holmes sighed and grudgingly stuck a bookmark in the book he had been reading all morning. His four year old brother, Sherlock, had recently chased off his third au pair this year, leaving Mycroft to care for the child. "Coming," he replied, his voice tinged with annoyance. After putting his book on the shelf, he stepped out of his room, into the hallway in search of the boy. "Sherlock?" he called, peering into his brother's room. It was empty- not a good sign. If he wasn't in his room, he was somewhere else in the house, causing trouble…trouble Mycroft would be blamed for.

"Mycroft! Come here!" Sherlock yelled from the kitchen.

"Please tell me you haven't destroyed anything important." he called back wearily, hurrying down the hall. The sight that greeted him made his heart sink. There was Sherlock, standing on a chair at the kitchen table, a green gooey substance covering not only the boy's hair and clothes, but the table and floor. "It exploded everywhere when I added the base! Isn't that brilliant?" He lisped excitedly, beaming at his older brother. Ever since Mycroft had come home for summer holiday with binders of chemistry homework, Sherlock had taken an interest. In an effort to keep him from hurting himself, their parents had bought him a children's chemistry set which Mycroft had been unable to separate him from since. Mycroft took a deep breath and pinched the bridge of his nose. "It's…brilliant." Sherlock repeated quietly, watching his brother with a small frown.

"What did I tell you about making a mess?" Mycroft sighed disappointedly, walking over to Sherlock and picking him up, careful not to get any of the sticky goo on his new shirt.

"Are you mad?" Sherlock asked, eyes downcast as Mycroft set him on the kitchen table. "I didn't mean for it to explode. I was just experimenting. Like you."

Mycroft grabbed a handful of paper towels and began cleaning the floor, getting on his hands and knees with a scowl. "I'm not mad," he said halfheartedly. "It's just… I told you not to make a mess. This…this is a mess and now I have to clean it." Mycroft said exasperatedly. There was silence as Mycroft mopped up the remainder of the floor. When he got up to toss out the dirty, sopping towels, he saw Sherlock, eyes trained on the ground. Fat tears were rolling down his pale cheeks and dripping onto his trousers, tears which he made a clumsy effort to hide. But Mycroft was too quick for him. After depositing the towels in the bin, he wiped his hands on his trousers and walked over to Sherlock, crouching down slightly to get to his eye level. "Sherlock," he said gently. "I'm sorry. I'm really not mad." He patted Sherlock's curls and wiped his cheeks, giving him a small smile. "Look at me," he said, tilting Sherlock's chin up. "You just have to be more careful, okay? But I'm not mad."

Sherlock nodded and sniffed, pouting his lip and looking up at his brother with big, blue eyes. "Promise?" he asked quietly.

"I promise. Now, how about you help me clean the table, then we can go outside and play?" Mycroft smiled, lifting Sherlock off the counter and onto the floor.

Sherlock nodded, taking a wad of paper towels from his brother and climbing up onto a chair, where he stood, wiping up the goo. After everything was cleaned, Mycroft threw the used towels in the bin and led Sherlock outside. By then, Sherlock had bounced back to his normal, chatty self. "…with the queen! Like us because we have a queen, too! We're like bees!" Sherlock giggled, rushing to his tree house and beginning to climb the ladder leading to the trapdoor.

"I suppose we are." Mycroft grinned, sitting on the ground at the base of the tree and watching his brother fondly. They stayed outside for the rest of the day, Sherlock in his tree house, playing pirates and shouting directions to an imaginary crew. Mycroft listened to him and laughed quietly at his brother's energy. Despite the fact that his brother was a nuisance, Mycroft Holmes couldn't imagine life without him. At the very least, Sherlock made his life more interesting…and who wants a boring sibling, anyway?

Not Mycroft. He was perfectly content with his loud, obnoxious, brilliant little brother.