Part one of the Lie To Me / Sherlock crossover.
Cal Lightman and Sherlock Holmes were called by the Scotland Yard to deduce a suspect for a string of serial killings. Cal believes he is a psychopath. After Cal’s examination, they chat.
Sherlock: Lestrade tells me you’re an ‘expert’.
Cal: Very hostile way of a compliment, yeah.
Sherlock: I don’t do well with competition.
Cal: Like Mary?
Sherlock: What are you talking about?
Cal: Oh come on, John told me about his recent engagement. When I went to look at your reaction I noticed the look of disgust on your face. You can tell a lot about a person when their friends talk about their relationships, am I right? When did you realize you were gay?
Sherlock: When did you realize you were in love with Ms. Foster?