To understand why any of it happened — the cruelty, the careful lies, the locked doors — you have to understand what our father left behind.

His name was Theo Larkin, and he had been a senior forensic accountant, a man who spent his life proving, with numbers, what people tried to hide.

He died of a sudden illness when Nora and I were fourteen.

And before he died, understanding the world more clearly than we did, he had done two careful things.

He had placed his life insurance and his corporate shares into an irrevocable trust, one designed to unlock only on our eighteenth birthday, so that no one could touch it before we were adults.

And he had left us that encrypted drive, and made his brother swear to look after us.