Title: The Minor Third
Fandom: Sherlock (BBC)
Rating: G
Length: 343
Summary: Sally Donovan explains Sherlock's cryptic remark

For the third time Greg Lestrade re-arranged the notes and pictures on the evidence board.  Whichever way the articles were displayed there seemed to be no discernible pattern.  John Watson gave him a sympathetic smile.  John then thanked Sally Donovan who had reappeared with more coffee.  It was unlikely the extra caffeine would make any difference, but at least drinking it gave them something to do while they stared at the board in frustration.

Suddenly Sherlock said, “You’re looking at it all wrong.  It’s the difference between a major scale and a minor scale.”

“What?”  Greg and John looked at each other, both hoping the other would show signs of knowing what Sherlock was talking about.

“Of course,” Sally answered.

The two turned towards her, hoping she would explain.

“It’s the minor third,” she said.

“Have you two started talking in code?” Greg asked.

“Both major and minor scales begin with the same two notes,” Sally began.  “The third is different in the two scales.  Then come the fourth and fifth; again the same note in both scales.  The sixth and seventh can vary even more, depending on whether it’s a harmonic or melodic minor scale.”

Sherlock was nodding happily and Sally continued, “We’ve been concentrating on all the different things Ferguson has been doing during the day, trying to build up a pattern, which is a bit like the sixth and seventh note.  Whereas what we should be doing is looking at the regular pattern to Ferguson’s day – the first five notes if you like – and trying to spot the one small change, the minor third.”

“Well put, sergeant,” Sherlock said.  “Yet further proof school music lessons have wider ranging value than some people seem to think.”

Greg re-arranged the evidence board again and then stepped back with a grin.  “There,” he said, pointing at one of the surveillance pictures which had been overlooked in their initial considerations.  “That’s what we’ve been looking for.  I somehow doubt our ex-army major is going to be impressed by being caught by a minor third.”