The Forlorn (2011)

Richa, a young lady moves in to a new apartment. Sambit, a psychologist, lives in her adjacent apartment. The previous occupant of Richa's new apartment is dead and Richa finds a diary of that person. Richs is an introvert and spends most of the time knowing about the previous occupant from his diary. Sambit finds gradual behavioral changes in her and Richa starts to experience hallucinations.