I am mechanical, John.
More often than not, Sherlock is certain that he has the advantage. Caring would only degrade his mind, and he cannot afford the cost. This much has always been true.
Then there are times when he is not so certain. He often looks at John and sees the comforting hand he places on someone's shoulder, or hears the comforting tone with which he speaks. Sherlock can feel the warmth that John possesses and so easily passes on.
John will inevitably glance up to meet his eyes and see nothing but the whirring of complex thoughts. In this moment, he realizes he is alone in his empathy. And yet, he still continues to believe.
No, Sherlock. You are a human being.
Sherlock sees no reason to bother with the feelings of others. It should be enough that he saves their lives. Must he accept their tears, their cries of relief, and their embraces?
John accepts these willingly. He tucks them away into corners of his soul, giving them a home. He exchanges them for his own tears, his own aches, and watches them depart in another's hands. Sherlock knows that such an exchange is an indication of weakness.
And yet, John's strength reverberates through him like the beating of a drum.
Don't make people into heroes, John.
Sometimes, Sherlock stops and listens to the beating of John's heart.
It is there, alive and fluttering, when they run down the streets of London.
When they solve a mystery.
When their laughter echoes through the halls of 221B.
It is in these moments that Sherlock is reminded of his own heart. Not alive, but dormant.
Hidden away, behind locks that seem to have no keys.
You do have a heart, Sherlock. I can see it.
Sherlock begins to wish that he could remember where he left the keys.
They have been lost for many years; tossed into dusty corners and left behind. Forgotten.
But Sherlock can feel the locks wavering under the pressure of his newfound companionship. And each time John's heart beats in sympathy for another, Sherlock's heart makes a feeble lurch.
You are the only one who knows where to look.
And then it all becomes too much.
When Sherlock cannot find the words to say, he seeks out the one who always can.
He finds John curled up in bed and slips under the covers without a word. He waits for John to speak, but hears no sound. Silently, an arm is wrapped around his waist, pulling him close.
John does not even open his eyes.
In the darkness, Sherlock allows the tears to fall.
No, Sherlock. It has been there all along.
He listens to the beating of John's heart and thinks of his own: raw and scarred from trembling powerlessly against the locks that encase it.
Sherlock knows now that the man beside him has offered him the keys. He need only use them.
As he leans into John's warmth and places a soft kiss to his cheek, the locks fall away, revealing a heart that beats with the strength of a man who is unafraid to feel.