Monsieur Blake had his back to the room when he was talking to you, so, it was perfectly possible for you to see her, the only person who could do so.
Разговаряйки с Вас, г-н Блейк е стоял с гръб към стаята и Вие сте могла да я видите, единственият човек, който е могъл да открадне отровата.