In fact he could have done all the things himself without any supernatural interference at all, if he had lied about where he was, for example when he goes to London. By the end you realise it is Faraday's own subconscious that is the culprit, and that either he or his ghostly subconscious form has murdered Caroline, but quite probably himself. The eerie and confusing ending of 'The Little Stranger' speaks to what director Lenny Abrahamson means by "haunted house."