2. Max
The second was not for a case, and John was actually rather happy for Sherlock.
It wasn't exactly typical for Sherlock to go out and meet new people, so it wasn't a surprise when she started with Max Hooper, the mousy young man from St. Bart's morgue who had been smitten with her for longer than John had known either of them.
Max was elated, of course, when Sherlock strode into the morgue bold as brass, crossed her long legs at the ankle, and asked him to dinner. He nearly banged his lower jaw against the table it dropped so quickly.
On her first date with Max, Sherlock wore what John had jokingly titled her "purple shirt of sex" and a merciless pair of slacks held in place by thin black braces. Not to be crude, but John thought she might attract just as many women as men in that get-up.
"Do I look all right?" she asked, almost sounding nervous if John knew better.
He smiled at her encouragingly. "You look like sex on legs, as usual, Sherlock." there was a knock on the door. "Now you have her back by midnight, sharpish, you hear?" teased John when the younger man smiled at him from the other side of the doorway.
His flatmate nodded gravely and flicked his ear before donning her coat and leading Max authoritatively down the pavement. Rubbing his ear, John shook his head with a smile and went upstairs for a cuppa and good book before turning in.
Sherlock tromped in at precisely midnight - waking John from the doze he'd fallen into on the sofa - threw her coat in the general direction of the wall hook, and crashed dramatically into what was typically John's unoccupied armchair.
"You know, I was joking about being back at midnight," slurred John sleepily, rubbing his face as he sat up.
She scoffed and rolled her eyes, toeing off her shoes, then slipping the braces from her shoulders and beginning to unbutton her shirt. "Believe me, John, your little joke was a life-saver," she huffed as she pulled the shirt off and pulled her hair loose, reclining in nothing more than a vest and trousers.
Instantly, John's protective side flared up, seeing how relieved Sherlock seemed to be home. "Max didn't try anything, did he?" he sharply asked.
"Don't be dull, John, of course he didn't," she replied. "Max means well, but he's boring and admires me too much to be taken seriously as a real romantic interest. As soon as the timing was appropriate I bolted."
"You won't even give the poor bugger a chance to get used to you?"
She narrowed her eyes at him. "I've known Max for five years, John. If he hasn't gotten used to me yet, he never will."
After a moment's consideration of how Max never had seemed to stop vying for Sherlock's attention over even the past year John had been back in London, he shrugged.
"Suppose you're right. Did you at least eat? I know you've been thinking over that missing grandmother case..."