Sherlock felt something had changed.
Normally, he scorned just "feeling" things. But this was different mainly because it was his feeling and his feelings tended to be accurate.
He felt an inexplicable urge to DO something. That he was special. He knew he was already a deductive genius, but this was special in a different kind of way. He had a feeling that he could save the world.
Naturally, this was a childish thought. He kept it to himself, no need to get John unnecessarily worried. But he did start doing Internet research about people with special abilities, people who were born to save the world.
A name came up. A mysterious name. Nothing seemed to show up except for the said name. Sylar.
Sherlock continued to research late into the night. He would find out about this mysterious Sylar, and he would discover why he suddenly wanted to become a hero.
Sherlock was sitting in Scotland Yard trying to explain to Lestrade that this was, in fact, important.
"He's a mass murderer, for God's sake! I can't even track him down? It would be fun!"
"It's in America," said Lestrade. "We don't work in America."
"Fine then, I'm going myself and solving this," said Sherlock. He stalked out of the office and hailed a taxi back to 221b.
"We're doing what?" asked John, for the third time in as many minutes.
"We're going to America to track down a mass murderer who only kills people with special abilities."
"Sorry, WHAT?!"
"God, John, don't you people have brains at all? Come on, we're going to the airport!"