Sherlock and Irene did not meet each other for the first time in Belgravia. They go back ten years ago to a 90s underground London drug scene. This was before they became Sherlock Holmes and Irene Adler and were just teen drug addicts and runaways, but were still two of the most brilliant people around. This is a Sherlock/Irene/Adlock prequel and a Sherlock prequel, the first chp.