In the continuing saga of the Corleone crime family, a young Vito Corleone grows up in Sicily and in 1910s New York. In the 1950s, Michael Corleone attempts to expand the family business into Las Vegas, Hollywood and Cuba.

Surveillance expert Harry Caul is hired by a mysterious client's brusque aide to tail a young couple. Tracking the pair through San Francisco's Union Square, Caul and his associate Stan manage to record a cryptic conversation between them. Tormented by memories of a previous case that ended badly, Caul becomes obsessed with the resulting tape, trying to determine if the couple is in danger.

A couple of high school graduates spend one final night cruising the strip with their buddies before they go off to college.