Tom Welles is a surveillance specialist-what used to be known as a "private eye"-but his version of the profession is hardly the stuff of which legends are made. He has a modest, home-based practice in Harrisburg, Pennsylvania, where he lives an existence remarkable only for its normalcy with wife Amy and baby daughter, Cindy. Respected but still waiting for a big break that will improve his professional status, Welles spends most of his time on routine cases involving unfaithful spouses and the like. Nothing too dangerous, nor too threatening... until a small, innocuous-looking plastic reel of film turns Welles' life upside down, sending him down a sordid and terrifying path into society's darkest corners. From the lurid sidewalks of L.A.'s Hollywood Boulevard to the squalor of New York City's meat-packing district, Eight Millimeter follows Welles as he relentlessly pursues a bizarre trail of graphic and disturbing evidence to determine the fate of a complete stranger-a girl who begins to haunt his imagination and conscience. Aided in his obsession by a streetwise adult bookstore clerk, Max (Joaquin Phoenix), Welles drifts away from his wife, family and former life. What Welles learns is beyond his worst nightmares, as he comes to realize how deadly a small reel of eight millimeter film can be.