When my daughter was 6 months old, I started noticing some unusual behavior. She would laugh and babble like someone was playing with her when no one was there. She would start crying and before I could even get to her, she would calm down and coo. I honestly didn't think much of it until I was up late one evening and caught a glimpse of a woman's reflection in a window. She was standing in the door between my office and my room -- the door that was originally the front door of the house. I could see her clearly, a tall woman with dark hair wearing an old dressing gown. When I turned to look directly at her, she was gone. It was unsettling, but I never felt a negative presence in our house.
The house was old and we were the first owners who hadn't been descendants of the family that built it. I ignored her for the most part, though her interactions with my daughter became more frequent.
The creepiest part was when my daughter woke crying in the night when she was almost a year old. My husband and I both got up to check on her but I heard something odd over the baby monitor and he grabbed my arm and put his finger over his lips. We stopped dead in our tracks and listened: there was the unmistakable sound of a woman singing a lullaby. Sure enough, our daughter quieted and said, "Night night." My husband ran into her room to check to make sure that she was alright. Everything was fine, luckily, but we cleansed the house the next day.