Ever since John learned about Sherlock carrying on with Irene. He knew this was odd. It wasn't like normal people, normal people had dates, met parents, went to antique stores. Formed relationships. Not Sherlock Holmes and Irene Adler. It wasn't a booty call, a quick and dirty once weekly or bi-weekly thing. They didn't live anywhere near each other. And Sherlock might be away for a good month or so, After it was arranged. One night when John was watching David Attenborough thing on tigers, it came to him. Sherlock had been pacing around one for a week, yes there had been a case, it was over with. But it some other kind of energy. A restlessness that feral, hormonal and awful. John noticed that lube he'd bought for personal, private use had been stolen, and someone not him had bought a six pack of tenga eggs on online, very sloppy right in the browser history.
"Why don't you chat up girl like a normal person?" Asked John on the last night.
"No! It can't be a girl, a normal girl would want normal things, boring things! I am not going clothes shopping, I'm not going on boring dates! I'm not-" Sherlock was by interrupted the sound of a woman's moan his phone, her ring.
He looked at the screen and smiled. "YES!"
"She's answered?" John said.
Sherlock's attention was on the screen.
"Jukkasajarvi, Sweden, the Ice Hotel for the starters. Hmmmm and there is serial killer the lose in that area, they haven't caught him.. yet. Oh that woman knows me!" He said giving a little jump. "Brilliant!"
And he went to his room to start packing. It was like this, always like this now. John felt he had joint custody of Sherlock now.
He was on the way out the door with a huge suitcase, when John said:
"Be safe?"
"Honestly, John she won't get pregnant, I had a vasectomy, that's not an issue anymore," Sherlock said.
"What? When?" John said
"Two visits ago, good-bye." Sherlock said and strode down the stairs.
John was left watching the tigers on Tv David Attenborough narrating. The tigers had finished mating, It was explained how tigers and most cats go on heat, have sex, then clean themselves throughly and go their own solitary way. That was Sherlock and Irene a week, maybe a month of sex and adventure and then they'd leave. Not to much contact, to not much intimacy. Just enough for when the need came. Then back to their own lives.