Even though John had broken up with Jessica two days ago when he found her sleeping with the guy next door, he still hadn't worked up the courage to go crawling back to 221B. He still couldn't believe that he'd spent two months with her, even moved in with her just to have her betray him like that. When he came home to see their neighbor in bed with his girlfriend he'd just gone to a hotel, putting off the inevitable return to Baker Street. He couldn't bear to hear Sherlock's "I told you so's".
Still, it seemed he just couldn't keep any of the Holmes men out of his life, because there was Mycroft standing outside the door to his room, umbrella in hand and customary scowl on his face.
"Dr. Watson." He stated simply and pushed his way into the room, looking about with some visible distaste.
"Um...hello?" John replied.
"We have something to talk about, please sit down." Mycroft sighed, his voice as lethargic yet regal as always. John realized that Mycroft was inviting him to sit even though he was the guest, but did as he said anyway.
"So...what is it? I didn't accidentally commit treason did I?" John joked lamely, wondering why else the important government official would suddenly turn up at his door.
Then it clicked. Sherlock.
Whenever Mycroft bothered talking to John at all, it meant Sherlock was in some kind of trouble and due to the Holmes brothers' ongoing sibling rivalry, Sherlock would accept no help from Mycroft.
"When have you last seen my brother?" Mycroft asked.
"Not for awhile actually...maybe last month? He's busy most of the time. Always working some new case." John's concern for his friend grew, he wished Mycroft would stop being so vague and get to the point. "Why? Is something wrong?"
"Well, I'll just say it's imperative that you return to your old lodgings immediately. I will settle the hotel bill, and you will leave now." Mycroft was infuriatingly blase about the whole thing.
"Hang on, what do you mean I'm leaving?" John asked. "You won't even tell me what's going on and you expect me to take orders from you?"
"Please, John." Mycroft pleaded, and that was something John wasn't used to seeing from him. "This needs to stay between you and me. We can't let anyone else know or the consequences for him would be terrible. Please if you care for Sherlock Holmes, you will go home to him now."
John stared for a moment, gaping, then nodded.
"A-alright...okay." John sighed. "So it's serious?"
"Indeed." Mycroft stood and walked to the door, then he turned. "Thank you for your cooperation, doctor."

John didn't know what to expect when he came back, after all no one knew what to expect with Sherlock. The man had a habit of walking into the room covered in blood and holding a harpoon for God's sake! So when he ascended the stairs to his old flat, his heart hammered in his chest.
Yes, he had no idea what to expect, but he certainly didn't think he'd be attacked upon entering the flat.
No one had answered to his knocking, so he'd just opened the door feeling familiar enough with his old place to come in uninvited. As soon as he'd set one foot through the door someone jumped him, hitting him across the back with a broom handle. Being around Sherlock and time in Afghanistan had guaranteed that John was no pushover, so he managed to recover quickly and swing around to block the next blow. He grabbed the broom and flung it away.
"What the hell was that?" he yelled, and then he froze, because his attacker was a pale thin man in a blue dressing gown-none other than Sherlock.
"I don't know how you found me, but be warned, if you try to kill me then we both go down." Sherlock snarled, and John took a second to look the man up and down to make sure his eyes weren't playing tricks on him. Yes, it was Sherlock, but he was a shadow of his usual self. Thinner than usual, disheveled, wild-eyed, something was definitely wrong.
"Sherlock, it's just me. Now calm down..." John put his hands up in a placating gesture. He tried to focus on this from a medical perspective, he had to ignore that his best friend just attacked him and try to find the reasoning why. Clearly Sherlock was not well, but why?
"I don't know who you are." Sherlock growled, eyes darting about...doubtless to find another weapon.
"It's me. John. Calm down." Dilated pupils, light sensitive no doubt from the way he was squinting, now check the wrists. Just as he thought, multiple puncture marks. Conclusion: Sherlock was using again. Enough so to make him delusional, paranoia was a dangerous side effect of cocaine, in this case more dangerous to John than Sherlock seeing as the detective was hell bent on hurting him.
"John left." Sherlock spat. "So who are you?"
"It really is me, it's John." John tried to scoot closer, if he could just subdue him...
"Prove it. Tell me something only John would know." Sherlock's eyes studied John, distrustful.
"Alright, what do you want to know?" John asked, taking another step, but Sherlock noticed this time and stepped backwards.
"Stay back." He hissed. "Now, tell me...what happened after we went to Dewer's Hollow?"
"You...got scared, and we got in a fight. Then you experimented with my tea. Sherlock it really is me." John insisted, and a spark of recognition appeared in Sherlock's eyes.
"...John?" He asked, his guard lowering just slightly.
"It's me." John stepped forward again. "Sherlock, let me help you." The detective's lip quivered, like a sad child. Then he flung himself at John and fell into his arms.
"John..." he sighed. "You came back..."
"Yeah, well your brother near threatened me, and I knew you couldn't take care of yourself so..." John tried to force a jovial tone into his voice, and tried to ignore the way Sherlock was shaking.
"Mycroft is always poking his nose where it doesn't belong." Sherlock scowled. "I'm fine. I've been under attack the past few weeks but besides that I'm quite fine."
"Under attack?" John asked, a bit skeptical.
"I know they're there. I still don't know who they are but they've come for me. How on Earth did you get past them, John? Heh, always the soldier. I bet you scared them off for awhile." Sherlock stood and glanced out of the windows as he said this, his grip on reality clearly slipping.
"Sherlock...how much have you been taking?" John asked, causing Sherlock to display a blank face.
"How much what?" He replied innocently.
"Sherlock, I know things seem a bit muddled right now, but try to think. There aren't any attackers, you've been taking cocaine. How much?" John pressed, walking up to Sherlock and gently placing a hand on his shoulder. Sherlock scowled again, glaring at John.
"Believe what you want." He said, pushing John's hand away and retreating to his bedroom.