Sanpietro, the reclusive concierge of an apartment building, has the keys to every unit. At night, he watches the lives of the residents from his dim, solitary studio; by day, he slips into their apartments, immersing himself in their routines and habits. But a chance encounter with the young son of a newly arrived tenant stirs something within him, driving Sanpietro toward a drastic act in his desperate attempt to ease his loneliness.
