David Lamont, a successful literary agent in New York City who is known to be ruthless toward friends, foes, and clients alike, moves into his new penthouse apartment.

As the days progress, the packages become more ominous, including DVDs that show David's every move, indicating he is being watched constantly.

He enlists the help of his friend and colleague, Rebecca Fay, and hires a private investigator, Detective Martin Soll, to uncover who might be behind the surveillance and the threatening messages.

As the investigation deepens, David learns about the apartment's dark history, which includes a series of brutal murders.

The tension reaches a climax when David discovers hidden cameras and evidence suggesting that someone has been living in the apartment with him unnoticed.