Sherlock is experiencing a host of symptoms that he can't explain. They come and go with no apparent rhyme or reason. He feels a combination of anxiety, tightness in his chest, difficulty swallowing, dizziness, flushing, nausea, and heart palpitations. It's highly inconvenient. A quick internet search leads him to determine he is experiencing one of the following: a heart attack, a panic attack, or allergies.

Obviously, he has nothing to be panicking over, so that can't be it. He'd like to ignore the possibility of a heart attack, but his past drug usage does put him in a high-risk category. Reluctantly, he decides he needs to consult John.

The detective yells up the stairwell, "John, I need you. I think I've been having heart attacks."

John comes jogging down the stairs. "What the fuck are you on about?"

Sherlock describes his symptoms which are profoundly worse when the doctor is in close proximity. In fact, they're so bad, he collapses on the sofa and rests his head in his hands.

"Alright. Okay. I'll go get my kit. Just take it easy," John soothes, trying to sound less panicked than he feels. When he comes back, he listens to Sherlock's heart, takes his pulse and blood pressure, then leans back, looking relieved. "Everything looks fine. Can you tell me more about these symptoms? When do you feel them? What triggers them?"

"I'm not having panic attacks."

"I never said you were," John soothes. "I'm just trying to understand what's going on."

The detective pouts for a bit, but he finally answers. "It happens mostly when I'm around you. Sometimes when I'm thinking about you. I don't know what that means."

John's mouth falls open. "You of all people haven't deduced it. You?" He starts laughing which instigates a full on Sherlockian strop. "No, no. Please, don't. Let me show you." He leans forward, closing the space between them, and brings their lips together in a kiss.

Sherlock doesn't respond for a moment. He breathes a quiet 'oh' against John's lips, then he kisses him back. He understands it all, and he understands that John feels the same way. He no longer feels all the disturbing symptoms from before, he feels an euphoric happiness that fills him from head to toes and promises to last forever.