This was back somewhere between 2015-2016 ish. My family and I are from Denmark, but since my father is an engineer we moved around a lot. During this time my father and my step mother and my sister lived in Qatar, and I would fly down to visit during holidays. One time, when I came to visit (and many times after that), I noticed a smell of smoke in the tiny hall between the kitchen and the living room. When I asked my step mother about it, she answered with "You smell it too?" -apparently my father had never noticed the smell, and thought nothing of it. That's when she told me about the many strange encounters she had had in the house. This included the smell of smoke in that one specific spot, seeing shadows move from the kitchen to the living room in the window reflections and my little sister, who was around 3 years old at the time, asking my step mother about the person smiling at her in her room from time to time. Moreover, they were always sick while living in the house. For example, my little sister had developed asthma, which she no longer has today. I get the chills just thinking about it. I never noticed anything else, which I was visiting other than that smell of smoke. They have since moved, and are now living in a different part of the world with no such encounters since.