I'm not sure specifically as there's not much information here. It could be a mystery related to Carson House's past, perhaps something like a long - forgotten family secret or a tragic event that took place there.
There could be a number of reasons. Maybe the real story has to do with a lost fortune that was somehow connected to the Carson House. If there was a treasure hidden there long ago and it led to a series of misfortunes or betrayals among those who knew about it, the house might seem to 'fear' uncovering that past. Another possibility is that the real story involves a broken relationship or a family feud that was so intense that it left a sort of negative energy around the house, and delving into it would be like opening old wounds.