John is starting to think that it's impossible for him and Sherlock to do anything without it turning into a situation straight out of a detective novel.

Sherlock is starting to wonder why the Mafia are so interested in one killer-for-hire (previous work in Moscow, Buenos Aires, Paris, and Berlin, about five foot three if Interpol's data was anything to go on, and a fondness for poisoned ceramic knives judging by his last three hits.)

He relays this data to John, who is so used to this sort of thing that he doesn't even bother to ask how he knows all of that. His only question is-

"So why do you think they're after him?"

"I'm not sure. Most assassins have a relatively short life expectancy- it isn't the safest working environment- but they're usually not bumped off without a good reason. You can;t go around killing all your assassins, or you've got to start outsourcing, and the Russians charge through the nose."

"So why do you think they're looking for him?"

"It could be any number of reasons, really… he could have killed someone he wasn't supposed to, he could have not killed someone he was supposed to, he could have been seen flirting with the Don's daughter, or…"

"Sherlock, that wasn't a good 'or'. Or what?"

"Or he could have picked the wrong side in a recent Sicilian power struggle, offed a high-ranking government official in their pocket, and fled to London with three million pounds worth of stolen jewellery, including a ring that previously belonged to Napoleon."

"Ah. So, what are we going to do? Are they serious about burning London?"

Sherlock looks a bit grim. "That code is used almost exclusively by the sicari- the elite assassins that the Mafia hire when things are serious. They're notorious for not really understanding the idea of overkill."