Meanwhile, while John was arguing with Mycroft Holmes about the etiquette of accepting a case and the stupidity of giving in to Sherlock's every whim, said detective was wandering around the streets of London without even really realising that John had gone. Every so often he turned on his heel and picked a different direction, muttering to his absent friend about the laws of probability and finding a crime.

He was desperate.

That was the long and short of it, he could barely bring himself to think that they might have to go back home after this with no new case. He would even take a robbery, even something as petty as a gang of hoodlums stealing a car radio at this point. At least it would take the edge off. And worrying about how to take the edge off was how he ended up following his feet towards the back end of Oxford Street where he knew one of his homeless network that dealt in a specific sort of poison.