John started noticing it after Sherlock had been called to crime scenes during the day. Sherlock avoided direct contact with the sun, mirrors and people when they were eating garlic, among other things.

One day, outside a crime scene, John noticed Anderson kept giving Sherlock hopeful, and worried glaces. It spoke volumes, even to John, who wasn't a genius like Sherlock. Finally, he pulled Sherlock to another room of the house, claiming he may have found something.

"Anderson has been looking at you all day."

"Obviously, John. I was wondering when you would finally notice," Sherlock replied dryly, looking around.

"Do you know why?" John felt a little exasperated at his friend, but kept his anger under control.

"Yes. I have been misleading Anderson for quite some time by setting pretences that I am a vampire."

John opened his mouth to say how ridiculous it was, before the last several crime scenes floated back Sherlock had avoided Sally Donovan like the plague, claiming she had smelled awful. John had came by, and had only smelled garlic on her breath.

"How long have you been doing this?"

"Several months, I have been hypothesizing on when Anderson will finally crack and bring a wooden stake and mallet to work with him."

John burst out laughing, "You're being serious, aren't you? But that doesn't answer my question."

"Yes. As to why Anderson is looking at me all day, I have several theories."

"And they are?" John prompted.

"He doesn't smell of garlic, nor are there any abundance of mirrors around. I have avoided direct contact with sunlight as I usually do."

"Have you shown any aversion to holy water near him?" John asked suddenly, remembering Anderson had looked extremely pleased with himself after Sherlock had laid a bare hand on the staircase railing leading upstairs.

"No, I have had no chances to-" Sherlock trailed off, and his eyes lit up, "That's it. He's waiting for me to have an adverse reaction to the holy water he put on the stairs. I thought the railing was a little damp."

"Why didn't you say anything?"

"I thought the cleaners may have come, the Yard has released the downstairs to them."

"So soon?"

"The victim was the daughter to a very rich retired politician, Lestrade is being pressured on all sides on this case."

"Which is why-"

"He called me. Back to the matter at hand. What would be a good enough reaction, do you think?"

"A chemical burn, maybe, but those could be-" John stopped as soon as Sherlock swiftly left the room. John hurried after him.

"Did you find anything?" Lestrade asked.

"No. John thought he saw something, but obviously he did not," Sherlock spotted the bathroom, and entered quickly, beckoning John in. He shut the door before Lestrade could say anything.

Sherlock opened the container of bleach he found under the sink, "What are you doing?" John asked, leaning against the door.

"I have a slight allergy to most strong chemical cleaners, John. I'm surprised Mycroft hasn't sent you my medical records yet."

"He has, but I haven't read through the whole thing yet. How bad is this reaction?"

"It is mild. I'll get a rash that will last a few days. I trust you will monitor it's healing progress?"

John nodded. Sherlock twisted the bleach open, and held his hand over the sink, palm facing up. He poured a fair amount of bleach on his hand. The detective made no sign of discomfort, despite the rapid redness spreading on his hand. He shut the bottle and rinsed his hand off when he was pleased with the results.

The hand was red, and irritated. John could tell by looking at it, it would develop blisters before the week was done. Sherlock examined his hand for a moment, before stepping out of the bathroom past John.

He walked down the stairs, coat billowing behind him. John followed, watching Anderson from the corner of his eye. Anderson caught sight of Sherlock's hand, and his face lost all colour.

They left the crime scene, John barely able to keep his expression in check as they walked right by Anderson.

When they got to a taxi Sherlock called, they looked at each other and burst out laughing.

"The next time Anderson shows up, we should take the mirror in the bathroom down," John suggested.

Sherlock snorted, "And move all the garlic we own into Mrs. Hudson's fridge."

"If we keep this up, I bet Anderson will break in less then a year," John said.

"I agree, I believe it may be quicker, however."

John nodded, "Fifty pounds? I win if it's closer to the end of the year, you closer to now?"

Sherlock nodded, "Yes."

(LINE BREAK)

I wrote this after seeing a post on Pinterest, saying that Sherlock pretended to be a vampire, with John assisting him in any way possible just to torture Anderson. I laughed a little too much at the prompt, and the plot bunny wouldn't leave me alone.