Cold Storage.

Cold Storage tells the story of a deformed young man who lives in a creepy dystopian high-rise whose inhabitants have lived there their entire lives, and never leave; they don't even think there is a world outside. He suffers from grim hallucinations and a growing urge to commit murder. A strange, malicious mass is growing on his wall, and making his visions worse, and a disembodied voice in the basement tells him to give in to his homicidal urges.