Sherlock knew.
But he didn't know it like he knew most things, which were based on facts and evidence.
He knew it before she was even born. He knew it like the animal instinct that told you to run - there was no other option.
He knew that his daughter had to die.
Every year since Ada Holmes had been born, they sent a sign that they were watching.
The first years, watching Molly cradle the sleeping baby, the fire sending up merry sparks in the living room. A neat pile of ash on the hearth.
Taking her to work, Lestrade telling the fascinated little girl about fingerprints. Ada, grabbing his hand and pressing it up to her smaller one, giggling. And ash, scattered over the crime scene.
Picking up a moody 10-year-old Ada from school, Molly gently scolding her for getting her uniform dirty. It wasn't mud from the playground - it was ash, dead black against her white shirt cuff.
A.S.H. Ada Sylvia Holmes. It was always going to be her, Sherlock's world, the one who could save him, and the one who could be turned into the weapon that could strike him down forever. Of course Sherlock knew. He had made enemies of the worst kind, the criminals and the monsters. And the only way they could truly stop him would be to get inside his mind, his fortress.
Now they could have the second best: his daughter, his genetics, who knew his mind better than anyone.
Sherlock had to protect her, and now it was time. It was simple, really; he and Molly had already faked one death. Surely a second wouldn't hurt...
