Sometimes when Joan and Sherlock argue, everybody wins. (Well, not them, but that’s the beauty of it.)
“And you don’t want your name to appear?”
“Not at all. The work is its own reward. Perhaps I shall get the credit also at some distant day when I permit my zealous historian to lay out his foolscap once more—eh, Watson?”
– Arthur Conan Doyle, “The Adventure of the Norwood Butler”
There’s nothing like a good fight between Sherlock and Joan.
It’s a delicate thing. A fight simply for the sake of shaking equilibrium won’t really hit home, and they’ve already been through so much as partners that several topics would have to be reintroduced in advance before the match began. (You can’t have Joan meaningfully confront Sherlock on a sobriety problem, for example, without addressing the swiftly-sidelined overdose from the end of season three.) But when Sherlock and Joan square off in “Henny Penny The Sky Is Falling,” it’s about their deepest and most fraught concern: The Work.