From: ep. 2.2
Line: SHERLOCK: You’re brown as a nut; clearly you’re just back from your holidays.
Reference: In A Study in Scarlet, the very first ever Sherlock Holmes story, Stamford says this to Watson: “Whatever have you been doing with yourself, Watson? You are as thin as a lath and as brown as a nut.” In ep. 2.2, Sherlock says the above to Lestrade, thereby nailing his real reason for being in Dartmoor.