Walled In (2009) on Netflix

Plot summary

Sam Walczak's first assignment from her father's demolition company is the Malestrazza Building, a remote apartment house she is to supervise for takedown, with a partnership promised if she succeeds. The caretaker, Mary, greets her, and Mary's teenage son Jimmy carries her bags and explains the rules: the eighth floor belongs to the architect and the roof is dangerous. Researching the address, Sam finds the building was a crime scene where sixteen bodies were sealed inside the walls, and Jimmy says his father was among them and that a local factory worker was blamed. When the lights fail on the eighth floor, Sam cuts her leg in the dark and Jimmy tends the wound. Her boyfriend then arrives, and Jimmy grows jealous.