Sam Walczak, a recent engineering graduate, is eager to prove herself as an employee of her family's demolition business. She is given her first assignment to oversee the demolition of a dilapidated apartment building located in a desolate area. Upon arriving at the building, Sam discovers that there are still tenants living in the condemned building. Sam tries to convince them to vacate the premises, but the tenants refuse and give her a tough time.
One of the tenants, a young boy named Jimmy, tells Sam an urban legend about a serial killer, Josef Malek, who used to live in the building and entomb his victims within the walls. Jimmy believes that the dead are still inside the building and that they harass the residents to this day. Sam does not believe Jimmy's story at first, but as she spends more time in the building, mysterious things start to happen, and she begins to realize that there may be some truth to Jimmy's tale.
As Sam continues to work on the demolition, she uncovers the secrets of the building's past and the true nature of Malek's twisted crimes. She also discovers that Malek's victims may not be as dead and buried as she initially believed. Sam soon finds herself trapped inside the building, fighting to stay alive and escape the sinister forces that are trying to keep her there.
As tension builds, Sam desperately tries to unravel the truth behind the building's dark history while trying to escape with her life intact. The movie climaxes with a terrifying showdown between Sam and the malevolent forces that dwell within the walls of the condemned apartment building.