Observance (2016)

In the grip of grief following the death of his young son, his marriage on the rocks and nearing bankruptcy, Parker reluctantly returns to work as a private investigator. Embarking on an unusual assignment to observe a woman from an abandoned apartment, Parker witnesses bizarre happenings surrounding her, unaware that the derelict building that he surveys her from has birthed a dark presence which slowly threatens to consume him.

Source: TMDb