The day Mary Watson invited Sherlock to tea, he was a nervous wreck.
It wasn't that he disliked Mary, though she was responsible for his broken heart; it was simply unusual.
Then again, their situation had changed.
Sherlock sat in his usual chair in their sitting room, tried not to notice her pallor. He politely asked how she was feeling, though it was a stupid question, considering.
Neither spoke while she openly contemplated his person. "I hated you. At first."
Sherlock inclined his chin. He'd not insult her by feigning ignorance.
"Hated the sway you hold over him," she continued. "Then, one day, I realised something. You're like me."
Sherlock was suddenly the recipient of that brilliant smile usually reserved for John. The one that made him hurt all over, made John's eyes crinkle.
"We have the same heart." She inhaled. "You see, hearts recognize like. Both of ours belong to John Watson."
Their eyes met; Sherlock's lips parted in disbelief.
"I'm okay with that," she whispered. Sherlock looked away.
"Don't let him forget about me completely." Instantly, reassurance was on his tongue; she raised her hand. "I'm expecting you to care for him. You were, perhaps, always meant to."
After Mary's funeral, Sherlock held John while he fell apart in his arms; tears on his cheeks, promises on his breath.