"She. Is. Infuriating!" Sherlock stormed down the stairs from what was now Astrid's room.
"Mmmm, she gets it from you," John murmured from the couch.
"Obviously she doesn't, John, she was raised by someone else; personality traits are not genetic."
"Oh, I wouldn't be so sure. What's got the two of you in a snit this time?"
Sherlock huffed as he flopped down on the sofa, in his usual sulking posture. One floor up, John fancied he could hear Astrid doing the exact same thing (with a bed rather than sofa). "I simply informed her that she cannot destroy my experiments willy-nilly because they're too messy for her tastes."
"What did she do, then?"
In a tone that left the Would you believe? almost audible, Sherlock answered, "She threw out a vital experiment because, and I quote, 'it was in the way of the worktop that I needed to use for supper and it looked like a bunch of dirty saucers, how was I to know it was important?' Imagine, John, dirty saucers. As though she isn't intelligent enough to tell the difference between a used saucer and several different types of fermentation!"
Ignoring the backhanded compliment to Astrid (but storing it away for a future moment of "I told you so") John offered, "Well, she obviously didn't mean to, though I agree she probably could have talked to you about it a bit better. But Sherlock, you have to be the adult here. She's your daughter, not your equal, as much as she can seem like she is sometimes. She's brilliant, yes, but she's only a teenager. You have to be the bigger person and the disciplinarian, or she'll never respect you."
The sitting room was quiet for a few moments as Sherlock absorbed John's advice.
"Then…what do I do?"
"Go talk to her about why it upset you so much, and work out a system so that nothing important gets thrown away again while still allowing her space to cook. I like that she cooks. It means I don't always have to do all the work to feed you up. She's a good kid, at heart. If you'll just explain calmly and rationally, she'll probably even apologize."
"Ok," Sherlock said, "Ok. Yes. I'll go do that then."
As Sherlock ascended the steps much more serenely than he'd descended just minutes earlier, John turned the page in his paper and settled back comfortably into his chair, safe in the knowledge that another crisis had been averted.