Watson: "Just met a friend of yours."
Sherlock: "A friend?"
Watson: "An enemy."
Sherlock: "Oh. Which one?"
Watson: "Well, your archenemy, according to him. Do people have archenemies?"
Sherlock: "Did he offer you money to spy on me?"
Watson: "Yes."
Sherlock: "Did you take it?"
Watson: "No."
Sherlock: "Pity, we could have split the fee. Think it through next time."