Watson: I just met a friend of yours.
Sherlock: A friend?
Watson: An enemy.
Sherlock: Oh. Which one?
Watson: Your archenemy, according to him. Do people have archenemies?
Sherlock: Did he offer you money to spy on me?
Sherlock: Did you take it?
Sherlock: Pity, we could have split the fee. Think it through next time.