There was this innocent looking granny that looked like the Medium from Insidious who turned out to be some woman in disguise. Throughout the years, she kept poisoning the son of this family with cookies so when I found out, I stabbed her 8 times in the back and 7 in the heart but she still managed to stay alive after I left the house! She wanted revenge so she called up the family's neighbours who were also 'old people' in disguise and they went on a rampage to look for me and the family!!
Near the end, the only way to kill them was to suck them up with a vacuum.