John Watson walked into his friend's flat to find Sherlock asleep on the couch with a woman about Sherlock's age watching him with a smile on her slightly parted lips. She had curly raven black hair, and was thin. She wore a leather jacket, a purple shirt and black leggings.
She turned towards John and held a finger to her lips. "Shh, Don't wake him. It's so rare for me to see him sleep while he isn't plagued by nightmares."
John stared at her and said "Who are you?"
"His sister Serenity." she smiled at him.
He smiled back and held out his hand "John Watson."
"I know." she grabbed his hand and he helped her stand. "Mycroft told me all about you."
"None of it is true." John flirted with the taller woman.
"All of it was good, well-deserved praise. Please don't tell him I was here?"
"Sherlock or Mycroft?"
"Both. Sherlock can't know about me and Mycroft would try to imprison me again."
"I doubt he could do it."
"I said try, not that he could."
They laughed quietly, and John gestured towards the kitchen "Care for some tea?"
Serenity smiled "Sure. Do you have any peppermint?"
As they sipped their tea, Serenity listened to John talk about Sherlock and his cases. After an hour, Sherlock groaned and turned over in his sleep. Serenity stood up and thanked John for the tea, walked over and ruffled Sherlock's dark curls before opening the window. She turned back towards John as she put one leg out the window. "Thank you for becoming his friend. He's had fewer nightmares since you've been here." She blew him a kiss before jumping out of the window.
John walked over and shut the window and muttered to himself as he watched Serenity walk down the pavement and disappear into the crowd "I think I'm in love." He smiled and looked at the two mugs of tea on the table, walked over and put them into the sink to wash.
Sherlock rolled over and looked at John tiredly "You had a girl over while I was asleep." he accused crossly.
"Nope. I didn't."
"Don't lie. I can smell lilac perfume, your tea and peppermint tea. You just washed two mugs, and you have that stupid lovesick puppy look on your face that you have when you get a new girlfriend."
John smiled at the thought of Serenity and replied "I guess you're right. I'm in love." He hummed as he finished washing the dishes and went into his bedroom and hoped that he'd see Serenity again soon.