"It's hereditary, you know."
Molly frowned at this. It was the first thing Sherlock had said in days, and it was not what she had been expecting.
They were sitting quietly (as usual) in the darkest corner of the backyard, strategically hidden from the eyes of her mother through the kitchen window. Sherlock had found this place pretty quickly upon his arrival to their home, and her parents had given instructions not to bother him. But Molly had looked up at her father, worry etched in her features and he nodded ever so slightly, giving her permission to approach the dark haired boy that was now living with them.
"What's hereditary, Sherlock?" Molly asked, trying to push down the hope that maybe now Sherlock would maybe want to leave this place and maybe go to the swings in the park down the street.
"You know," Sherlock lifted a finger to his head and made the swirling motion that so many of the kids of school did behind his back. Of course he knew they did it, but he said nothing. It made Molly angry to see it.
"Stop it, Sherlock, don't call it that," she snapped, glaring at the ground. "It's wrong."
He shrugged in response and hugged his knees once again. "It's true. I was reading it in the library. I have a 'genetic predisposition' increased through my mother's side. At any moment, I could just snap and start killing people." He snapped his fingers together in a loud click that made her flinch.
He saw her jump and she felt her stomach clench at the look on his face. He thought she was afraid of him.
She grabbed his hand, squeezing harder when he tried to pull away. "You're not going to snap, Sherlock. You're not." She scooted closer and made sure to catch his eyes. "I won't let you, ok? You're not like your mum at all, Sherlock, and I promise nothing like that is ever going to happen."
He should have scoffed. It's what he did whenever her mother was kind or when her father gave him a sympathetic pat. But he didn't do that with her.
Sherlock looked at her with wide eyes and Molly would later recall they looked like they might have been filled with unshed tears.
"How do you know?" he whispered, almost as if he didn't want anyone to hear him voicing his own fears.
"Because you're a good person, Sherlock. And you're smart and brave and really really good." Molly grew frustrated at not being able to find the right words, the words that would show him that she believed in him, that the horrible things that had happened had nothing to do with him, that it wasn't his future.
"But it could happen," he retorted, despair entering his features.
She squeezed his hand again. "No it won't. Not if we're friends. Not if we're together, ok?"
It was a stupid promise to make, one that was based on nothing more than the faith of a ten year old that still didn't understand the way the world worked.
But it didn't matter.
Because in that moment, Sherlock believed her.
He squeezed her hand back.