Anthony is a mystery. I'm taking a wild stab in the dark here, but I'm guessing Anthony knew beforehand what the Shadows Manor was like. (Ie. before he came to Shadows House, he wasn't as deeply influenced by the soot in the villages. And he realized that the children who went to Shadows House died. Maybe he even intentionally entered the House to try and make a change. Or alternatively, he had a close bond with Christopher, and after the brainwashing broke, he orchestrated a plan to end Shadows Manor... There might even be a possibility that he killed Christopher! So mysterious!)