Days turned into weeks, and weeks turned into months, and Sherlock found something curious happening to him. At first he pushed it away, because these were the things that he had sworn to himself he wouldn't let happen. But they did, and before long, they took over:
The thought of the bow tie man would make him strangely uncomfortable in a comfortable way. He would be undeniably happy that the man existed, yet irreversibly sad at the thought that he was not here. Sherlock didn't know enough about human emotions to understand from the beginning what was going on. He started accepting less and less cases. As the gap between the now and his meeting with "The Oncoming Storm" grew larger and larger, the murders became more boring and one-sided. His job was grey, his life was grey, everything was grey, except for him. He shone in every colour of the rainbow, and the thought of him made Sherlock Holmes' heart heavier and lighter all at once. That same heart the ex-army doctor had believed was cold and hard softened and accelerated whenever he thought of the man in tweed with the waistcoat, which was far from being a rarity. Sherlock had only seen him for about three minutes and grown so attached to him in that time. He wished he had known how much he'd need to see him later on; he could have easily stopped him from getting into the blue box, demanded answers before the most remarkable man in the high-functioning sociopath's life disappeared. Why didn't he stop him from leaving? The pain caused by his absence was becoming so deeply unbearable. He had never experienced such a thing before.
Could it be that the bow tie man felt the same? That the bow tie man was looking for Sherlock just as much as he was for him? Did the bow tie man's heart also yearn to see him? Was it so hard for him to find him again? If Sherlock couldn't track him down, why would "The Oncoming Storm" be able to track him down? Maybe they were connected somehow, and Sherlock was in such a pain because it wasn't only his own solitude.
Of course, there was also John... John's obliviousness about the whole thing comforted him. Sherlock never mentioned the bow tie man to him and concealed his sorrow at any moment he felt observed. It made it less hard for him. Still, all he managed to conceal was why he was so upset.
The few times they still spoke made him forget, but he had locked himself into the world of "The Oncoming Storm" and all he wanted was for the man he most longed to see in the universe to be in there, too. The few times Sherlock slept, he dreamt of meeting him again, of the bow tie man taking him by the hand and showing him the inside of that mysterious police box. He explained to him how the green device worked, and then, they would both disappear with the box, and fly away from London and from his work and from the dullness that was Earth. Some nights John came along too, but he was always the unimportant part of the dream.
If one would look at Sherlock while he dreamt, they would find him with a wide smile upon his face. A smile that he never wore whilst conscious. He was never this happy when he was awake, because every morning, he had to come to the cold realization that the dreams of the man with the green device who had stolen his heart since the very beginning had still not returned to save him from this nightmare. Filled with melancholia Sherlock continued his day-to-day life. The life he had chosen to avoid boredom was now drowning him in it, with only someone who could throw him a life raft and revive him. But that someone wouldn't come. And so he was left floating in the infinite, lonely ocean, drifting away from everyone he had once cared for. Of course John had tried to pull him out of his trance, with little success. Sherlock was still obsessed with the idea that if he would talk to anyone about the man who had visited him that day in March he would lose him completely, because then the tweed man would not only live within his fantasy but within the fantasy of every other person whom he told about him. He couldn't let that happen. He couldn't let the one thing that kept him going right now, the only hope he still had slip away from him any more. He knew he was out there somewhere looking for him, and he knew that one day they would meet again and everything would fall back into place. Quite simply: the bow tie man was Sherlock's and Sherlock was the bow tie man's.
The moment he realized this a thought crossed his mind, which at first he didn't want to admit. But soon it became too clear for him to act as if it wasn't true:
Sherlock Holmes had fallen in love with the bow tie man.