Sherlock was confused when Lestrade pulled him aside one time at a crime scene, in the bathroom off to the side where the body was. Usually he just let Sherlock come in and do his thing, sighing while The Idiot Yarders went about their idiot ways and tried and failed to insult him. Sherlock deduced that this had to do with John, because Lestrade looked worried about Social Norms and usually John was the one who cared about them. Lestrade told Sherlock that the killer was serial. Sherlock told him that Yes, This Was Obvious as those were the kinds of killers that Lestrade usually called Sherlock in for. Lestrade told him that this killer had a pattern and that that pattern was people whose sexes and genders did not match up. Sherlock did not understand the problem about this for 1.3 seconds then realized that this might mean that the John's Secret might not be a secret anymore very soon. Because Normal People were often stupid and bigoted John did not talk about Kaitlyn Watson that much, because he feared ruin. Ruin of what Sherlock did not understand, he usually deleted a lot of the questions people asked them, because they were unimportant.
Sherlock asked Lestrade how the Moronic Duo were taking it. He said that Donavan was taking it fine, she actually has some intelligence you know, but that Anderson was refusing to take the case. Sherlock said that maybe it would be a good idea for Lestrade to tell John this, it might be a nasty surprise. Lestrade told Sherlock that it might not be a good idea for John to be there because there weren't that many transgender people in anywhere and this killer probably worked at someplace like a hospital where he had easy access to public records. Sherlock said that they should ask John first because John did not like it when Sherlock went off and did something On His Own. Also John could protect himself, remember he was in the military.
So Sherlock went back to where the body was (in the living room) and asked John if he wanted to continue on the case. Donavan looked confused but Lestrade told her to leave and as she probably expected this anyway, she left. John said that he did not care that this was the killer's pattern, Sherlock Was An Idiot and probably would get himself killed or at least very nearly shot if John was not there. Lestrade asked John if he had told anyone besides Sherlock that he was Kaitlyn. John said that the only person outside his family and his psychologist was the doctor who had treated him after The Explosion That Revealed Things To Lestrade and Mycroft had threatened him with ruin to keep him quiet. Lestrade said that it was probably that the person who had killed these people was not a doctor because there were gruesome attempts to "fix" the them but these attempts made them look like they had been put through paper shredders. Sherlock said that hope was irrelevant it did not stop the facts. John said that he knew that, but John Was Vaguely Normal and so he felt things like hope and things.
Sherlock was very interested in finding out who the killer was because a)this was the most interesting case he had in a long time b)Sentiment made him want to eliminate any chance that John was Not Safe. Sherlock realized that of the things that all the corpses had had in common when they were breathing was that they all went to the place for their therapy. Not the same psychologist, the same secretary for all the psychologists. That secretary was in a relationship with one of the shrinks and he thought that maybe they were cheating on him so he planted bugs in all the rooms of the psychologists. That is how he found out that these people did not match sexes with genders and a strange case of Religion=Homicidal Tendencies he had been convinced that transgender people were abominations created by the Devil and that he had been sent on a holy mission by God to kill them all and try to fix them and make them repent of their sins in that order.
While they were chasing the killer he recognized John and started screaming about devil spawn and tried to repeatedly stab him. John hit him. Sherlock started laughing and kissed John. The killer than started spewing more Society Lies about Hell and a few other things that were possibly religious but that Sherlock had deleted a Long Time Ago. John hit him again. That is how the Yarders found them, Sherlock and John giggling like morons and the killer lying on the floor moaning/babbling in Latin. Lestrade decided that he did not want to ask, he had one Holmes that he continually dealt with on a daily basis who found it hilarious when North Korea threatened to kill America and possibly had the ability to depose said government, and he did not want to have to deal with the other one. The killer who apparently was more of a moran than Sherlock had originally thought thought that the coppers were coming to arrest Sherlock and John for their sins (did he think that Victorian law still applied in this area?) and that God was happy on this day.
When Sherlock and John got home John looked sad. Sherlock asked John why he looked sad. John said it was because he had thought that people had become smarter in the past 200 years but that in fact they had not. Sherlock said that in his opinion John was very smart and so was Sherlock and that it was just the idiots who believed Society Lies who were idiots and that humans were not all stupid. John looked surprised when Sherlock said this. Sherlock said that if all humans were stupid then his work would be terribly boring because stupid people murderers are very easy to find. John laughed and said that that was the Sherlock he was used to. He then went off to type up the day's case (though possibly on a file saved on his computer and not uploaded to the blog) and Sherlock went off to check on the tonsils he had put in the freezer inside some ice cube trays.