Burnt Offerings (1976) on Netflix

Ben and Marian Rolf rent a grand old country mansion as a summer getaway for themselves, their twelve year old son Davey, and Ben's Aunt Elizabeth. They feel they can't turn down the rent deal offered to them by the house's owners, siblings Roz and Arnold Allardyce, despite some reservations. First amongst those reservations, they are to take care of the house on their own, which Ben feels is too big a job, especially for Marian and the interior housekeeping. In Marian's words, the large size of the house is a "waste". And second and perhaps more important amongst those reservations, the Allardyces' aged mother will be staying in her room at the house, the Rolfs who are to provide a tray of food left outside her room three times a day, which Marian vows to take care of on her own, with no other members of the family to go into that isolated wing of the house so as not to disturb Mrs. Allardyce's peace. Upon their arrival at the house for the first day of their stay, they find a note from Roz and Arnold stating that they had to leave on an emergency, only with the necessary keys enclosed with no address or telephone number where they can be reached. As the summer progresses, the family members individually begin to exhibit unusual and unexplainable behavior, and unusual and unexplainable things start happening around the house. The strongest behavior ends up being Marian's total focus on renewing the house into what she says she wants it to be, or so she implies she is doing. These occurrences threaten both the loving family dynamic as well as the individual lives of the four. The answers to what is happening may be who or what lies behind the closed and often locked door of Mrs. Allardyce's bedroom.