Moriarty told him that he'd burn the heart out of him. And when Sherlock arrived to see 221b Baker Street on fire, he knew that the burning had begun. Mrs Hudson was stood outside her sandwich shop, staring through the window as the fire raged on angrily. There was no hope. The fireman had told him so. Everything was gone. Sherlock remembered feeling something slightly akin to sorrow or despair. He really had liked this flat. He was vaguely aware of Mrs Hudson whispering in his ear, apologising silently, but he never stopped to listen to the rest of what she had to say. He had to find John.
When John hadn't arrived on the scene as the smoking ruins of the flat had been hosed down, Sherlock was confused. Not panicking, there was no need for that. Not yet. When he didn't reply to his texts, Sherlock's mind whizzed over the possible explanations: No money to answer. John was on a contract. No battery left. John kept his phone on charge overnight so as to avoid that very problem. He'd left it somewhere accidently. John bloody loved that phone. Which meant that it wasn't on John's person deliberately. Sherlock began to feel the first pangs of fear; tiny ones, clawing at the lining of his stomach, scratching at the back of his head.
Hours passed, and John didn't return. The clawing and the scratching intensified. Sherlock wanted to play his violin, but the bloody fire had burnt it. The sun rose and shone weakly through the windows of the café that he was sitting in, and John still wasn't back. He tried texting again. No reply. He tried ringing.
Hello, you've reached John Watson, please leave a message.
John, it's me, Sherlock. Don't you know it's rude not to respond to texts? Get in touch.
He didn't get in touch. Now Sherlock was worried.
Moriarty told him that he'd burn the heart out of him. Sherlock knew that Moriarty knew his weaknesses. He'd known them from the moment John had stepped out of the changing room in the pool. That split second of doubt, betrayal, sadness. That was Sherlock's weakness. John was Sherlock's weakness.
As he walked past his flat, Sherlock was aware of some paramedics looking slightly concerned. He looked back at the house, then back to them. He thought nothing of it. Idiots. Mrs Hudson came up to him and patted him on the arm, asked him if he was alright. Of course he was. He wasn't that upset about the house. She looked at him, slightly confused, then sighed gently and walked away. When you're ready to talk, I'll be here.
Sherlock stood looking up at the flat as it groaned and creaked under the wind. One more try, John. One last phone call. As Sherlock pressed 'ring' he heard an answering call coming from around him. Oh, so John had finally shown his face. He strode off towards the end of the road, following the ring, but it got quieter. So he was near. He turned and walked back, closer and closer to the ring. He could hear the ring right behind him. About bloody time, John. He spun round and found himself staring through Mrs Hudson's kitchen window.
The ring was coming from inside.
Suddenly, Mrs Hudson's mumbled apology came stumbling back to him. Snatches and phrases every now and then, jumbling themselves up inside Sherlock's mind.
They tried dear, but the door was damaged. He was a hero. He ran in, shouting for you, wanting to get you out. He saved my life. They were just too late for him. I'm so sorry, Sherlock.
John was inside.
All of a sudden, Sherlock's chest was on fire. He wanted to scream, cry, shake. Anything. The world wheeled and flexed around him and his head was searing. This wasn't right. This wasn't supposed to happen. But it was. Even Sherlock knew that. This was exactly what was supposed to happen.
He burnt everything. He burnt John.
Moriarty told him that he'd burn the heart out of him.