Everywhere John went, he felt like he was being watched. It was a quiet nagging sensation at first, but as time went on all the warnings in his head got louder and louder. He brushed it of as Mycroft or paranoia.
Time went on and it just got worse. He started watching his surrounding, and he picked out a face that seemed to appear a lot. He watched for it wherever he went, and he usually saw it. He tried not to let on that he knew. He assumed it would only make things worse. The man watching him didn't make any moves though, and the feeling of an imminent threat soon slipped from his mind. He never saw him too close to home, and the man just watched him, nothing more.
He brought it up casually as he was stitching up Sebastia's leg, trying to keep her distracted. She quirked an eyebrow, but said nothing more.
John was headed home from the pub one evening when he heard a clatter in an alley. He peered into the darkness and could just make out two silhouettes against the wall in a decidedly unromantic fashion. He was just drunk enough to be okay with heading down the alley to investigate, shouting at the figures.
"Oi, what's going on here?" He recognized his little spy, who was pinned to the wall, but he couldn't quite place the masked assailant until he caught a flash of green in her eyes. He cocked his head to the side. "What are you doing?" He heard her groan.
"Just go home, John."
He shook his head and crossed him arms over his chest. "No. Tell me what you're doing."
Even with her mask on her could picture the scowl on her face. "I'm taking care of something."
"This is the guy I told you about."
"You think I don't know that?"
He paused, looking lost for a moment. "Why are you doing this?"
"Because I can, John. Now go home."
He opened his mouth to protest, but she cut him off sharply. "Now, John." He sighed and pressed his lips into a firm line and he turned and walked away. He wasn't sure if it was the alcohol or the knife in her hand or the bite in her voice, but he didn't feel like arguing the moral high ground with her at the moment. He trudged home, collapsing into bed.
He wasn't followed again.