One of his fishes is missing.
Brilliant.
John was prepared for this to happen since Harry gave him a fish tank and a bag of fishes at his birthday four months ago. He made Sherlock promise explicitly that his fishes were not to be harmed or experimented on. John had hoped then it would be enough for Sherlock to ignore the fishes. Clearly, he was wrong.
He quickly sends off a text.
Where are my fishes? J
A reply comes back almost immediately.
They were exactly where you left them when you went to bed last night. SH
One of them is gone. What have you done with it? J
It is safe with me. Need it for a case. SH
Oh god.
YOU PROMISED NOT TO EXPERIMENT ON ANY OF THEM! J
I didn't use it for an experiment. SH
Another message arrives just as John plans to ask exactly how else Sherlock would need a fish otherwise: Must go. Suspect just left his office with a black canvas bag. Will explain tonight. SH
John at least knows better than to force a reply after that. He tells himself not to think about the missing fish at work, but when he is ready to go home he's bursting with curiousity. Sherlock had better be at home and ready to explain.
Thankfully, Sherlock is waiting for him by the front door of 221 Baker Street. They head inside and climb up the stairs into their sitting room. John turns around, ready to ask when Sherlock pulls out a clear plastic jar with a wide metal cap from one of his coat pockets. The missing fish is happily swimming inside.
Well.
Sherlock walks towards the fish tank, unscrews the cap and pours both water and fish back into it. Sherlock stares after it for a while before he speaks.
"I am sure you remember that I once liked to talk to the skull. I also told you that you were a better alternative than the skull. When I was…" Sherlock keeps staring at the fish intently. "When I was away, I got into the habit of speaking to objects that reminded me of you. When I returned you were once again here for me to talk to, but you are often at work and I don't want to upset our tentative peace. So I chose an object of yours to speak to. The fish seems to work best so I have taken to carrying it. You didn't notice before because you are already at work when I scoop it out from the tank."
He looks up at John now, face curiously expressionless. John is not fooled in the slightest, and thinks for a moment before he smiles gently, "you could ask again, you know. I would have come with you to help in any way, work or no."
"Oh." Sherlock smiles, "I shall keep it in mind next time, then."
No fish has left the tank for a case ever since.