In the weeks before the Reichenbach hero jumped to his death, before Sherlock Holmes disappeared out of John Watson's life, graffiti started appearing around London. IOU, it said. Just three letters. Most people just thought it was a particularly bold tagger. IOU, on walls, in the Tube, carved into park benches. The one near their home on Baker Street had wings around it. Sherlock had sneered when he noticed, but John wasn't sure why.

John knew what was behind it, of course. He had found the apple, forced the story of Moriarty's visit out of Sherlock. IOU. John hardly slept those weeks, between running around solving cases and anxiety over when Moriarty would make good on his claim.

IOU

The letters haunted him.

After...after. After the fall, the funeral, after John's whole world came crashing down, while he was still sleeping on Harry's couch, more graffiti started appearing around the city. The first one he saw was tiny, scrawled in black permanent marker on the inside of a toilet stall door.

I BELIEVE IN SHERLOCK HOLMES

John felt like someone had punched him in the stomach. He left the store as fast as he could, cursing for the hundredth time his limp and his cane, getting a cab, and almost giving the cab driver his Baker Street address before he remembered. He went back to Harry's (who was spending the day with Clara) and spent the rest of the day curled up on the couch, watching crap television until the ache lessened (it never truly faded) and he fell asleep.

Two days later he was walking to St. Bart's for his shift when he saw some city workers trying to clean paint off of the side walk. They had gotten a few letters off, but most of it was still readable.

I ELIEVE I SHERLOC HOLM

He smiled a little, sadly, even though it hurt. Sarah asked him how he was doing, and he desperately wanted to tell her that he wasn't crazy, that he wasn't the only one who was standing up for Sherlock.

The next day, he got a text message on his phone from Lestrade. It was a picture from what John recognized as the skate park he and Sherlock had visited during the banker case. Writ large and clear, almost in a space of honor among all the spray painted scrawls was the same message:

I BELIEVE IN SHERLOCK HOLMES.

He rang Lestrade.

"Do you know who's doing this?" Lestrade said by way of greeting. "It's not you is it?"

"It's not me. It's just as much of a surprise to me as it is to you," John replied.

"Yeah, well they're all over the bloody city," Lestrade said. "They've got me investigating all of them."

"Punishment?" John asked.

"Yeah. I'm no one's favorite right now. Well, just thought I'd call. Let me know if you hear anything."

They traded pleasantries for a little while longer before they both had to get back to work.

After that, John started noticing them more and more around town. He found one written in chalk in front of his work. He found one scrawled on his receipt for a cup of coffee, on a bench he passed every day, on the back of a bus. Every single one of them hurt, but the punch in the gut was starting to feel like someone punching the air in victory.

Maybe he wasn't crazy.

The day that Lestrade had called a second time John went to Baker Street, well after dark. Each and every wall was coated with paint, with chalk, with flyers. Their...his front door was layered with then, the stoop covered in flowers. He picked his was through them, silently unlocking the front door. He knew Mrs. Hudson had to be asleep and he didn't want to bother her.

John instinctively reached for a gun he didn't carry when Lestrade spoke.

"I figured you'd come here."

"So you sat here in the dark, waiting?" John asked, turning on a lamp.

"Yeah, well, I didn't want anyone to know I was here," Lestrade replied. John went to the desk, looking at the mess. He wanted to survey the kitchen, check the fridge, but he couldn't bring himself to do it. "I haven't touched anything."

"Neither have I," John said quietly. "Why are you here?"

"Because these messages are driving me mad. They've got me running around the entire city. They're starting to pop up in Scotland and Whales too. I've travelled between London and Cardiff three times this week," Lestrade said. John tilted his head, the question clear on his face. "I told you, punishment. They can't do anything to me directly because all of the cases and the evidence have come back in the proper order so far, but they can make my life a living hell while they work."

"So you came here?"

"Yeah, well, so did you."

John didn't reply, knowing Lestrade had a point.

"But all these messages have given me an idea," Lestrade said, holding up a can of spray paint.

John just stared at Lestrade in shock.

And then he smiled for the first time in weeks.

It wasn't the finest, or the most beautiful, but it was true.

I BELIEVE IN SHERLOCK HOLMES