While rewatching Season 2 episode 1 of Sherlock – Scandal in Belgravia, I noticed something that I had not seen before. Besides a continuity error where Martin Freeman’s legs were crossed and then they were not, I noticed that Sherlock had a lipstick mark on his cheek.
I think that we can all guess the story here. While returning Sherlock’s coat, and reprogramming his phone, Irene couldn’t help giving him a little peck on the cheek. If Sherlock had noticed this, maybe he could have solved the puzzle of her password a little bit faster. Ya think?