Anderson: I believe in Sherlock Holmes.
DI Lestrade: Yeah, well, that won't bring him back.
Sherlock: I didn't know you spoke Serbian.
Mycroft: I didn't. But the language has a Slavic root. Frequent Turkish and German lone words. Took me a couple of hours.
Sherlock: You're slipping.
Mycroft: Middle age, brother mine, comes to us all.
Mycroft: Baker Street? He isn't there anymore. It's been two years. He's got on with his life.
Sherlock: What life? I've been away.
Sherlock: Interesting thing, a tuxedo. Brings distinction to friends and anonymity to waiters.
Mary Morstan: Gosh, you don't know anything about human nature, do you?
Sherlock: Nature, no. Human... no.
Sherlock: London. It's like a great cesspool into which all kinds of criminals, agents, and drifters are irresistibly drained. Sometimes it's not a question of who. It's a question of who knows.
Mycroft: We have solid information. An attack is coming.
Sherlock: Solid information? A secret terrorist organization's planning an attack? That's what secret terrorist organizations do, isn't it? It's their version of golf.
Mycroft: Don't be smart.
Sherlock: That takes me back. "Don't be smart, Sherlock. I'm the smart one."
Mycroft: I am the smart one.
Sherlock: I used to think I was an idiot.
Mycroft: Both of us thought you were an idiot, Sherlock. We had nothing else to go on. 'Til we met other children.
Sherlock: Oh, yes, that was a mistake.
Mycroft: Ghastly. What were they thinking of?
Sherlock: Probably something about trying to make friends.
Mycroft: Oh, yes. Friends.
Sherlock: Rest assured, Mycroft, whatever this underground network of yours is up to, the secret will reside in something seemingly insignificant or bizarre.
Mrs. Hudson: Yoo-hoo.
Mycroft: Speaking of which...
Mycroft: I'm not lonely, Sherlock.
Sherlock: How would you know?
John: I wanted you not to be dead.
Sherlock: Yeah, well, be careful what you wish for.
John: I'm definitely going to kill you.
Sherlock: Oh, please. Killing me. That's so two years ago.